Fleshed out specs for Uniform Buffer Objects
Added return type table for getActiveUniformBlockParameter
Add tests for struct equals.

Struct equals is a current problem area in ANGLE, where it doesn't
currently handle any type of non-trivial struct. Particularly
structs containing vectors, matrices, arrays and nested structs are
broken currently.
Merge pull request #594 from jamiemadill/struct-equals

Add tests for struct equals.
Removed unneeded enum
Merge pull request #592 from toji/uniform_buffer_spec

Fleshed out specs for Uniform Buffer Objects