Using CONSTANT_CASE for geometry type
Using PascalCase for geometry enum values

This adds a bit more inconsistency to the library, but we didn't have complete consistency before.  Almost all existing string enum values are lowercase (a couple are camelCase and one is dash-separated).  The closure library isn't consistent either (with case for enum properties or values).  I imagine this could be justified in saying someone could blindly use GeoJSON type values in places, but in the end, you'll need to read the docs before guessing right.
This commit serves no purpose other than helping minimize a diff
Marking the geometry type enum as stable
Merge pull request #1335 from tschaub/geometry-type

Change geometry type enum and mark as stable.