Add curved geometry support: CircularStrings and CompoundCurves

GeoTools 12 recently added limited support for curved geometry.  This pull request adds GeoScript wrappers for CircularStrings and CompoundCurves.
Yes, a GeoTools CompoundCurve is also a LineString.

http://docs.geotools.org/latest/javadocs/org/geotools/geometry/jts/CompoundCurve.html

The CompoundCurve linearizes whenever a JTS op is called, so they just work.