Separate indexed and non-indexed paths in GfxDevice. Non-indexed should be usable as before
Using u16 for indices in GfxDevice to improve portability
Optimized buffer writes, now avoids some checks that are already performed by GfxDeviceVertexWriter and virtual call. Overall speed-up is about 15% in synthetic sample.
Fixed the conflicts and brought it into the fallguy repo (feature/spine) before realizing I need to remove Spine from the community repo. See my comments on Slack.