Add support for import and export of floating tables.

Add support for shapes, and especially for shapes with textual content. 
In OOXML, shapes are represented by the wps:wsp element, and shapes with textual content by <wps:txbx>, <w:txbxContent>.
Such shape can be added to a Word document using the Insert -> Text -> Text Box -> Draw Text Box, or through a shape's context menu -> Add Text.

Do not confuse these shapes with Text/Rich Text content controls (see https://feedback.telerik.com/Project/184/Feedback/Details/190057 )

When exporting, an option of how to create the PDF bookmarks should be provided:
- Using the RadFlowDocument bookmarks
- Using document Headings

The image in the header is not exported to pdf.

Workaround: Use version R1 2022 where this is working.

Office Open XML defines a mechanism for the storage of content which is not defined by this Office Open XML Standard, for example extensions developed by future software applications.

The stored data could be an image.

Exception when there are merge fields in the header/footer and one performs mail merge: 

Unable to cast object of type 'Telerik.Windows.Documents.Flow.Model.Header' to type 'Telerik.Windows.Documents.Flow.Model.BlockBase

The attached sample project below demonstrates a possible workaround for PAGE and NUMPAGES fields when exporting to PDF. The demo shows how to generate document from scratch containing PAGE and NUMPAGES fields and export it to PDF.

Find and Replace document elements with special characters.

• ^p - Paragraph Mark
• ^t - Tab Character
• ^? - Any Character
• ^# - Any Digit
• ^$ - Any Letter
• ^^ - Caret Character
• ^u - Section Character
• ^v - Paragraph Character
• ^c - Clipboard Contents
• ^n - Column Break
• ^+ - Em Dash
• ^= - En Dash
• ^e - Endnote Mark
• ^d - Field
• ^& - Find What Text
• ^f - Footnote Mark
• ^g - Graphic
• ^l - Manual Line Break
• ^m - Manual Page Break
• ^~ - Nonbreaking Hyphen
• ^s - Nonbreaking Space
• ^- - Optional Hyphen
• ^b - Section Break
• ^w - White Space

When inserting a section between two paragraphs the section parent is not correct.

Example:

Paragraph paragraph1 = editor.InsertParagraph();
Paragraph paragraph2 = editor.InsertParagraph();
editor.InsertSection();
Paragraph paragraph3 = editor.InsertParagraph();

Expected:

paragraph1.Parent == paragraph2.Parent
paragraph2.Parent  != paragraph3.Parent 

Actual:

paragraph1.Parent != paragraph2.Parent
paragraph2.Parent  == paragraph3.Parent