User defined CRS

This is the second incarnation of the GeoTiff writer. In addition to handling CRS with an EPSG authority code, it is also capable of writing out all other CRS as "user defined". It does not check the input CRS to see if an EPSG code could describe it more succinctly. However, each component of the CRS is separately examined for an EPSG code, and this code is used if found.