The canvas snapshot test should use glQuery 2.0
Automatically create the `gl` alias for glQuery if it is not already present
Fix the canvas snapshot test
Update the glquery-ext extra module which includes the new canvas snapshot extension
Keep track of the existing canvas, so that it is not recreated in glQuery (all canvases that point to the same rendering context should be shared)
Add callbacks to the canvas `start` method
Add a test for drawing fullscreen quads
Fix a bug in the scene normalization routine
Add the fullscreen quad test to the index
Test for a scene with a subarray of tags