Strongly-typed enums for ES 3.0 (complete)

Implemented sectiosn: Pixel Rectangles. Binding & Managing Framebuffer
Objects, Renderbuffer Objects, Attaching Renderbuffer Images to
Framebuffer, Attaching Texture Images to Framebuffer, Framebuffer
Completeness, Invaildating Framebuffer Contents, Renderbuffer Object
Queries, Simple Queries, String Queries.
Merge branch 'master' of https://github.com/thefiddler/opentk