Delete WebGL buffers
Merge pull request #25 from elemoine/webgl-point-delete-buffers

[webgl-point] Delete WebGL buffers
Add unit tests for WebGL image replay
Merge pull request #26 from elemoine/webgl-point-tests

[webgl-point] Add unit tests for WebGL image replay
Fix texture coordinates in WebGL image replay
Merge pull request #27 from elemoine/webgl-point-texture-coords

Fix texture coordinates in WebGL image replay
Use "discard" in image shader

This leads to better looking Timeline profiles in Chrome's developer tools!
Add global opacity support to WebGL image replay

vectorLayer.setOpacity() now works as expected.
Add "color" support to WebGL image replay

This adds support for layer brightness, contrast, hue, saturation.