Minor texture item refactoring
Cache model parse results to resolve crippling slowdown in UpdateModels
Move texture transparency into a flags enum for future flexibility
Add support for dynamic per-tool sidebar controls
Add sidebar control for selection tool
Added setting to hide the 3D transformation widgets
Fix bug in the rotation widget where the pivot point could not be moved in the front and side views
Replaced hack-y VTF transparency check with VMT check (needs shader implementation to prevent unwanted alpha channel rendering)
Removed forced transparency from Source tool textures as they have alpha channel in their VMT