Removed TODO comment that was already done.
Body will now also be parsed from OpmlDocument.
Implemented Body parsing logic.
Moved re-usable function GetChildElements from the Body class into the OpmlElement base class that all OPML element classes should inherit from.
Implemented base recursive Outline parsing.
Added text attribute parsing to the Outline element.
Also made the value of the text attribute for an outline mandatory.
Added type attribute parsing for the outline element.
Implemented isComment attribute parsing vor the outline element.
Implemented isBreakpoint attribute parsing for the outline element.
If an outline is a comment, all descendant outlines are automatically also comments.