Use vertex buffer objects

Simon Ser requested to merge github/fork/ascent12/gles-shaders into master

Created by: ascent12

These are just some pretty mundane changes to the GLES renderer. In my extremely limited testing, using VAOs/VBOs instead of uploading the same vertex data over and over lowers the CPU usage slightly. There is still a lot more to do, but this is a start.

There are also some minor changes to cleanup the shaders.

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