Table of Contents - Completion

[AnonymousWalker]

This PR completes the functionality of creating Table of Contents (TOC) which was not working normally before.
After digging into the way Microsoft Words generates TOC and updates it, I found that there are two requirements:

1. The styles.xml in the .docx file should have those "Heading..." and other stuff that the TOC needed to look for and update pagination.
2. Obviously, we need to set style for the paragraphs that need to be included in the TOC: "Heading{#}"

Before: xwpfDocument.CreateToc() will produces

Press Shift + F9 to see field:

---

After:

Shift + F9:

Sample Code:

            var outputFile = "output/dir/location/filename.docx"
            XWPFDocument newDoc = new XWPFDocument();

            XWPFParagraph newHeader = newDoc.CreateParagraph();
            newHeader.Style = "Heading1"; // for TOC entry
            newHeader.SpacingAfter = 200;
            XWPFRun headerText = newHeader.CreateRun();
            headerText.SetText("Matthew");
            headerText.FontSize = 24;

            newDoc.CreateTOC();

            using (Stream str = File.Create(outputFile))
            {
                newDoc.Write(str);
            }

Reference: WycliffeAssociates#5. This fork is maintained by our organization and it's actively being used for converting different format to .docx