Fix projection doc
Merge remote-tracking branch 'origin/master' into projection-doc
Tweak doc
Removed =undefined for optional parameters
Removed default credits when constructing the CesiumTerrainProvider. The Terrain Server will provide proper attribution.
Merge pull request #1723 from AnalyticalGraphicsInc/undefined

Removed =undefined for optional parameters
Merge pull request #1721 from AnalyticalGraphicsInc/projection-doc

Fix projection doc
Merge pull request #1725 from abwood/terrainCredits

Removed default credits when constructing the CesiumTerrainProvider.
added new czm_depthRangeStruct and czm_depthRange constant.
fixed typo in capitalization
Merge pull request #1726 from gbeatty/glDepthRange

Gl depth range
Fix whitespace
Merge remote-tracking branch 'origin/master' into readonly-scene