Fixes potentially incorrect OpenGL state at startup.

We now explicitly call vsRendererState::Force() after beinging the
OpenGL context into being.  This fixes a *very* tricky bug when running
on OS X, and drawing something very simple as the first object rendered.
(may possibly occur on other platforms?  Probably more GPU-related than
OS-related, honestly.  Regardless, fixed now.)
Notes to self regarding improvements to sprite drawing.

No real change here;  just a little cleanup, and some notes regarding to
how to improve sprite drawing.  (The same notes also apply to model
drawing)