MOAI 2.0 - Documentation updates, CHANGELOG.md, etc.

[seclorum]

For MOAI 2.0 we need to do a full sweep of the documents (doxygen comments) as well as basic project necessities, such as the much needed CHANGELOG.md that documents the differences between the 1.5/1.6/1.0 and 2.0 versions of MOAI.

• - Doxygen comment update
• - CHANGELOG.md update
• - README.md update
• - HOWTO.md intro for new developers on how to get started

All existing docs should either be removed from the 2.0 release, or brought up to date (and maintained) to be sure they reflect the state of things with MOAI 2.0.