GeoJson fixes and cleanup

1. Automatically set `perPositionHeight` to true if a polygon contains altitude values.
2. Remove `sourceUri` parameter from the geometry functions since they are no longer used (and haven't been for a while).
3. Move polygon creation code into a helper function to de-duplicate code that was in both `processPolygon` and `processMultiPolygon`
4. Added specs and updated CHANGES.
Lighter theme for NavigationHelpButton added
Added import for the new css
Merge pull request #2159 from macoda/master

Lighter theme for NavigationHelpButton
Initial commit of maki icon set.

See https://github.com/AnalyticalGraphicsInc/cesium/wiki/Maki-Icon-Generation for details.
Merge branch 'maki' into simplestyle
First cut at GeoJSON simplestyle implementation.

Also introduce a `PinBuilder` which will serve as a generic way to generate
consistently styled placemarks for use in billboards.
Ongoing PinBuilder work.

Fix race condition that was preventing Firefox from working.  IE still broken due to cross-origin issue.
Ongoing PinBuilder work.

1. Change pin to a rounded box instead of a teardrop.
2. Add `Color.brighten` and `Color.darken`.
3. Avoid using SVG directly in order to make things work on IE.
4. Support single character labels as part of the geojson simplestyle implementation.
Add specs for new functionality.

1. Color.brighten/darken
2. GeoJson simplestyle handling.
Ongoing PinBuilder work

Mostly doc and Sandcastle examples.
Also add GeoJson.fromUrl to make loading more terse in some cases.
Add new GeoJSON example that exercises all simplestyle icons.
Add specs for PinBuilder

Fix GeoJSON code which I broke with last commit.
Tweak examples, update CHANGES.
Update CHANGES
Delete uneeded sandcastle example.

Fixes #2146
Merge pull request #2163 from AnalyticalGraphicsInc/delete-profile-halfdome

Delete uneeded sandcastle example.
Merge pull request #2148 from AnalyticalGraphicsInc/geojson-heights

GeoJson fixes and cleanup
Merge remote-tracking branch 'origin/master' into maki
Merge branch 'maki' into simplestyle
Make Sandcastle autocomplete work without combine step.

Sandcastle had an uneeded dependancy on `Build/CesiumUnminified/Cesium.js`
(generated during the combine step) since the `Source/Cesium.js` file could
provide the same functionality (and is created during the build step).

This means that for a fully functionaly sandcastle you only need to run
`build` and `generateDocumentation` which is way faster than
`combine and generateDocumentation`.