[FNA] Add #regions - Media Directory

Grouped by Type/Visibility.  Some Constructors/Dispose grouped together
where it appeared appropriate (which I'm thinking it usually is if they have the
same visibility).
Merge pull request #172 from 3vi1/monogame-sdl2

[FNA] Add #regions - Media Directory
Couple region changes to Media
I committed this before traveling and I should be ashamed
Merge branch 'monogame-sdl2' into mgsdl2-glshader