add TransformFeedback
Merge branch 'master' into transform_feedback_20
fix compilation of transform feedback (ref 20)
fix compilation of transform feedback (ref #20)
Merge branch 'transform_feedback_20' of github.com:cgcostume/glow into transform_feedback_20
Merge branch 'master' into transform_feedback_20

Conflicts:
	CMakeLists.txt
remove autobind in TransformFeedback when using begin/pause/resume/end
Made Transform Feedback destructor virtual (ref #20)
Add reading access for FBO attachments, add ::fromSource to Shader
Merge branch 'master' into transform_feedback_20
add documentation for TransformFeedback (ref #20)
Update Transform Feedback documentation (refs #20)
Import glow examples from other project
Merge branch 'master' into transform_feedback_20
Merge branch 'transform_feedback_20' of github.com:cgcostume/glow into transform_feedback_20
Merge pull request #24 from cgcostume/transform_feedback_20

Transform feedback 20
Add abstract log interface (ref #3)
Add virtual destructor to LoggingInterface
Add doxygen comments to logging classes
Add global verbosity level to filter log messages, add Info level, rename info to query