Workaround to skip binding missing RenderBuffers rather than asserting

For a Dota2 trace there seems to be a snapshot bug that is not capturing all of the Renderbuffer state associated with FBs.  Upon restore I'm hitting an error due to various RB handles being invalid.  This change works around that error for the time being until root cause is fixed.
Initial addition of SSO API Tracing

This adds basic, buggy support for tracing SSO API calls.
Still needs further debug, but it at least allows a DOTA2 Source2 trace to be captured without reporting errors.
Remove some debug code.
Merge pull request #150 from tobin-lunarg/initial-sso-and-rb-restore-workaround

Initial SeparateShaderObject support and Renderbuffer restore workaround