Fixed a bug where the Button was attempting to process invalid inputs.
Minor code styling.
Fixed places where I was initializing the Checkbox and hadn't accounted for some UI API changes.
Minor Code styling updates.
Cleaned up a lot of the Debug drawer and linegroup code.  These code cleanups resolved the known issues with the debug drawer and closes #105 .
Merge branch 'master' of github.com:BlackToppStudios/Mezzanine