Bug fix: Table.SetDirection(Direction) now changes the Direction of the Table and not just its contents.

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Created an abstract class called DocXElement and made every document element such as {Table, Row, Cell, Paragraph, Run, Text, etc} extend it.
Created an abstract class InsertBeforeOrAfter which is derived from DocXElement. This provides functions for inserting, page breaks, Paragraphs and Tables before and after self.
Moved Text and Run inside Paragraph, keep consistancy with Table which contains Row and Cell.
To Do: Investigated why the Picture class had two internal constructors. I removed one.
Added a _ to each .cs file that does not contain instanceable types, {Enumerations.cs, Extensions.cs, etc}

Bugs fixed
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Cell had a parameter Paragraph, this was incorrect as paragraphs can contain multiple Paragraphs. Now it returns a List<Paragraph>
InsertDocProperty now returns a DocProperty instead of void.

New features
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InsertDocProperty now contains overloads for the parameter track changes.
Cell now contains a Shading property, this can be used to set the background color of a cell.

Cathal: Added overloads to ReplaceText for Format checking and replacement.

Joel: Added Row.MergeCells
Joel: Added Row.Height property
Joel: Added Cell.Width property

A huge thanks to Joel: The first user to submit working & tested functions\properties for inclusion in DocX.