Merge remote-tracking branch 'upstream/master' into cesium

More changes required. Code does not compile.

Conflicts:
	src/objectliterals.exports
	src/ol/iview3d.js
	src/ol/projection/epsg3857projection.js
	src/ol/view2d.js
Fix compile errors in cesiumlayerrenderer.js
Make imageryLayer_ always defined
Remove addLayer and removeLayer
ol.Coordinate and ol.Extent are now arrays
Add cesium extern to ol-all.json
Fix cesium example
ol.Coordinate is an array
Create layer renderers
Fix compile error
ol.Coordinate is an array
Reset canvas size in frameState
Update frustum aspect ration on canvas resize
Make Cesium.Promise type explicit
Check for presence of Cesium
Add missing dependency
Snapshot