Add support for character spacing. Implement UI in the FontPropertiesDialog allowing to adjust the spacing between characters

The property in controlled by w:spacing element in OOXML specification.

The background-color attribute could be used for setting a background.

When a preceding paragraph's size is increased, for example - font size is changed, or paragraph is split to two, then the selection of the consequent paragraphs is wrong. When the cursor is on the second line and attempt to select some part of it with the mouse is made, the first or the third line is selected.

Steps to reproduce: 
1. Create two paragraphs with multiple lines
2. Insert new paragraph after the first paragraph
3. Try to select second line of the third paragraph with the mouse

Observed result: First line is selected instead of second line being selected

Multi-byte Unicode characters can be represented as multiple ANSI characters in the form \'xx, for example:
\'89\'ce can represent the character 火 if multi-byte encoding should be used. Using multi-byte encoding could be set explicitly using the \ucN tag, or implicitly using the \fcharset for the current font (e.g. \fcharset134 is double-byte).

When such text is imported (commonly CJK text [Chinese, Korean, Japanese] the characters are imported incorrectly (as two '?' or as two different characters for each character)

Such RTF documents are produced from Office 2010 (Word, Outlook), WordPad - on saving or on copying content from the applications.

Such behavior is observed when copying text from WPS Writer (version 11.2.0.10132) Part of WPS Office.

In MS Word the users have the ability to embed different objects and files in the document, using the Insert tab -> Text section -> Object. Implement similar behavior in RadRichTextBox, allowing to embed objects as inlines, to edit them, and to re-embed them after editing.

Add Paragraph property controlling  whether SpacingBefore / SpacingAfter is applied between paragraphs with the same style.

In MS Word, the corresponding option is controlled with "Don't add space between paragraphs of the same style" checkbox in the font properties dialog - and the paragraph spacing after will not be applied. 

In OOXML, it is described with the w:contextualSpacing element. We don't respect this property on import of such files, and the paragraph spacing is bigger.

Common use case for this feature is that when list is applied to multiple paragraphs, Paragraph List style is applied to the items, and this style has "Don't add space between paragraphs of the same style" applied, so the vertical spacing between the items is smaller.

Currently invalid attribute values, including invalid or empty values in CSS attributes in the 'style' attribute, could cause importing property with incorrect value, or NullReferenceException (the document cannot be imported).
Examples:
----------------------------------------------------------
<table width=”*”>
	<tr>
		<td>More Random Text</td>
	</tr>
</table>

The table is imported with 0 width. Instead the width should not be set.
----------------------------------------------------------
<table style="font-size:;">
	<tr>
		<td>More Random Text</td>
	</tr>
</table>

NullReferenceException is thrown.
----------------------------------------------------------

Workaround: replace the invalid values before import:
string importString = html.Replace("font-style: ;", "");

Improve measure and arrange of a document and its child document elements respectively - Span, Paragraph, Table, Section and etc. This will also improve the import time for large documents.

Characters like 🙋🏻 are not imported correctly and instead result in a series of question marks.

Fix available in LIB Version 2018.2.716.

IME: Cannot type in RadRichTextBox using Microsoft Pinyin Input Method (Chinese)

Add support for fallback font families on import, e.g. style="font-family:trebuchet ms, helvetica".

When Charformat is used as a general switch the formatting of the first letter of the field name is applied to the whole result.

Also, consider implementing \*MERGEFORMAT - This switch applies the formatting of the previous result to the new result. For example, if you select the name displayed by the field { AUTHOR \* MERGEFORMAT } and apply bold formatting, Word retains the bold formatting when the field is updated to display a new author name.

Introduce support for import/export of form feed character ( "\f")

There are cases when it is unwanted to be able to add words to a custom dictionary. In that case the DocumentSpellChecker should not create a custom dictionary in the IsolatedStorage and this should be reflected in the default UI: 
1. SpellCheckingDialog - the buttons "buttonAddToDictionary" and "buttonEditCustomDictionary". 
2. ContextMenu - the item "Add to dictionary". 

Changing the preferred width of columns to percentages from the Table Properties dialog actually sets them in pixels.

Steps to reproduce:
1) Insert a table

2) select table column property and set preferred width to 20%

3) press "next column" button and set preferred width to 20% 

4) Go to previous columns 

Expected: Column width is set in percentage.

Actual: Some (or all) columns have width set in pixels.

Copy/Paste Adobe Reader snapshots are displayed as blank images.

Support PDF/A when exporting. 

More information at wikipedia: http://en.wikipedia.org/wiki/PDF/A .

Workaround: Currently, the exported PDF document could be imported with RadPdfProcessing and exported with one of the supported PDF/A levels ( http://docs.telerik.com/devtools/document-processing/libraries/radpdfprocessing/howto/comply-with-pdfa-standard ).

Implement export of RadDocument's Bookmarks to PDF's bookmarks.

A digital signature can be used to authenticate the identity of a user and the document’s contents. 

We could export the image absolute position as CSS style, for example: ".img{position: absolute;left: 100px;top: 150px;}"

Additionally we could export the left, top, right and bottom margins of the image, as we already have this information in the model.