Add ofMesh load and save docs.

Added basic documentation for both load and save—this resolves issue #226.
updating fbo documentation
Merge branch 'master' of https://github.com/openframeworks/ofSite
Adding Seattle meet
Added documentation for ofBackgroundGradient()
corrected documentation for ofBackgroundGradient()
Merge pull request #227 from bschorr/master

Added Documentation to ofBackgroundGradient().
added documentation to ofClear
Merge pull request #228 from bschorr/ofClear

added documentation to ofClear