Improved GPU Cache

[davids91]

Stretch goals not met with #45 :

• Performance improvements
• Unittesting wherever possible
• Buffer update range improvements
• Fixing OCbit based "Missing data" display
• Caching Bricks in advance when there is capacity for it
• Handle when the tree is updated after the view is created
• Sometimes node requests are just stuck in one place
• Eliminate needlessly redundant data from OctreeRenderData: octree_meta, node_children, node_ocbits ( re-check each field )
  • Data to be uploaded shall be sent through a node update package with references to avoid unnecessary copying
• Make sure there are no new requests sent before the previous requests are written out ( use render data content to check if changes are uploaded )