Add gitignore
Cleaned up project files

Deleted OpenTK .dll - it is now referenced as a NuGet package
Updated project files to use NuGet Automated Package Restore
(http://docs.nuget.org/docs/workflows/migrating-to-automatic-package-restore, http://docs.nuget.org/docs/reference/package-restore)
Changed QuickFont project to target .Net 4.0 (full rather than client profile).

Sidenote - Updating OpenTK NuGet package fixed a bug where no textures were displaying.