Rich text display, Mercurial support, improve split window support

[byates]

• Change the code display window so that it supports simultaneous fixed space and variable spaced fonts and multiple font sizes: rich text display.
• Add an option to decode and display in-line any comments which contain doxygen tags, embedded HTML tags, etc.
• Add in-line display of embedded COM objects (ex: doc or visio) or images (use comments to contain the reference or data)
• Add mercurial support 
• Add hook for writing user extensions in .NET primarily for doing complicated dialogs and user windows
• Improve split window support.  It is too easy to 'break' the connection between windows and the divider takes up too much room.