flipped plane to match latest genmesh
move to an indexed plane
Merge pull request #290 from csherratt/fix_mesh

Update terrain for latest genmesh
Implemented prototype Light & Heavy batches in a separate module.
Implemented draw_batch
Implemented Batch trait for both light and heavy variants.
Ported the examples to use batches
Added docs, cleaned up the code
Cleaned up old Program trait. Improved comments.
Implemented Graphics class, added HeavyBatch typedef to shader_param, moved examples to the Graphics
Renamed batches to RefBatch and OwnedBatch