Port the geometric part of J2D-renderer to a "rendering-targeted" ISO 19107 implementation

The J2D renderer contains a library of geometric classes optimized for rendering. Those classes are not really J2D-renderer dependent and can be refactored in their own geometric package. We should move them in some org.geotools.geometry subpackages and make them implements ISO 19107. Proposal:

• org.geotools.geometry.array
  Would contains the current org.geotools.renderer.array classes,
  after we make them implement GeoAPI's PointArray interface.

• org.geotools.geometry.rendering
  Would contains the current org.geotools.renderer.geom classes,
  after we make them implement GeoAPI's Geometry sub-interfaces.

It would allows those classes to be used by other renderer implementations than J2D one. It may also help to turn the API into something more familiar to external developpers, since it will match a more standard one.