Rename ol.renderer.canvas.VectorRenderer

To be consistent with our naming convention, this one should be
renamed to ol.renderer.canvas.Vector.
Merge pull request #1088 from ahocevar/rename-vectorrenderer

Rename ol.renderer.canvas.VectorRenderer
No longer group features by symbolizer type

With symbolizer literals now being geometry type specific, we no
longer need the overhead to query the RTree separately for each
geometry type and render symbolizer groups by geometry type.

The geometry type index of the FeatureCache is no longer needed.

The filtering functionality of the FeatureCache's
getFeaturesObject method can be removed because it is no longer
used.