Rename ol.Projection to ol.proj.Projection
Rename ol.ProjectionLike to ol.proj.ProjectionLike
Rename ol.ProjectionUnits to ol.proj.Units
Limit ol.proj exports
Export ol.proj.Projection.prototype.getExtent for use in WMTS example
Merge pull request #955 from tschaub/proj

Move projection to ol.proj namespace and limit exports.