Add ST_Rotate

Note: By default, PostGIS rotates a geometry about POINT(0,0), while
GDMS rotated the geometry about the center of its internal envelope.

TODO: Allow the user to rotate a geometry about an arbitrary point, via
        ST_Rotate(Geometry geom, double theta, double x0, double y0)
        ST_Rotate(Geometry geom, double theta, Geometry pointOrigin)
Allow rotation about an arbitrary point
Fix some naming problems from copy-paste.
Add ST_Scale.

Note: In GDMS, we had the function
        ST_Scale(geom, scale)

In PostGIS, we have the functions
        ST_Scale(geom, xScale, yScale)
        ST_Scale(geom, xScale, yScale, zScale)

I.e., in GDMS, we assumed xScale=yScale. I decided to undo this
unnecessary coupling and also allow the user to scale the z-coordinate.
This amounted to conforming to PostGIS.
Merge pull request #31 from agouge/affine-transformations

Add affine transformations (ST_Rotate, ST_Scale)