Move various files to their new homes.
Move a bunch of terrain-related types to Core.
Sort requires.
Remove Scene dependency in TilingScheme.js.
Factor Renderer/Scene stuff out of TerrainProvider.
Update CHANGES.md.
Fix test failures.
Fix require order.
Merge pull request #1713 from AnalyticalGraphicsInc/moveTerrainToCore

Move terrain to core
Merge remote-tracking branch 'upstream/master'