Add support for creating Tables and applying tables styles (predefined ones or custom).

When imported in the WordsProcessing model, the current HTML doesn't respect the defined column width and all columns have identical width:

    <colgroup>
        <col span="1" style="width: 33.3302%;">
        <col span="1" style="width: 17.5658%;">
        <col span="1" style="width: 49.104%;">
    </colgroup>

Observed result:

Expected result:

Workaround: use the width property as follows:

    <colgroup>
        <col span="1" width="33.3302%">
        <col span="1" width="17.5658%">
        <col span="1" width="49.104%">
    </colgroup>

This is preserved in the xml once saved from MS Excel:

XlsFormatProvider: InvalidOperationException is thrown when importing a document with an unsupported BIFF record.

Workaround: Re-save the file with Excel before importing it.

After merging several PDF documents, some pages are blank indicating the following error:

The current formula: 
<c r="A1" s="1">
<f>[1]BILANS_JI!$C$2</f>
<v>22611518.026189998</v>
</c>

• Simple direct reference to a single external cell [1]BILANS_JI!$C$2
• No function, just a linked cell

The expected value to be returned is 22611518.

The issue is reproducible with PDF form fields and setting Polish characters to the text fields: e.g. "ęóąśłżźćń" 

Edit mode in RadPdfViewer:

Exit edit mode:

Here is a sample code snippet for reproducing the case without UI:

            PdfFormatProvider provider = new PdfFormatProvider();
            RadFixedDocument document = provider.Import(File.ReadAllBytes("file.pdf"), TimeSpan.FromSeconds(10));

            foreach (RadFixedPage page in document.Pages)
            {
                foreach (Annotation annotation in page.Annotations)
                {
                    if (annotation.Type == AnnotationType.Widget)
                    {
                        Widget widget = (Widget)annotation;
                        var field = widget.Field as TextBoxField;
                        if (field != null) 
                        {
                            field.Value = "ęóąśłżźćń.";
                        }
                    }
                }
            }
            string outputFilePath = "result.pdf";
            File.Delete(outputFilePath);
            File.WriteAllBytes(outputFilePath, provider.Export(document, TimeSpan.FromSeconds(10)));
            Process.Start(new ProcessStartInfo() { FileName = outputFilePath, UseShellExecute = true });

Add support for strikethrough font effect for cell formatting. Currently this is not supported by the model and is omitted on import.