Wkb adapter

This pull request adds a WKT decoder, and toWKB() exporting method to all geometries. I tried my best to port this functionality from [phayes geoPHP](https://github.com/phayes/geoPHP), changing what had to be changed to follow gisconverter logic and exceptions.

I added proper tests and helper methods too. 

If it's well received, I'm planning to add support for big endian (XDR) binaries, and GEOS function like simplify, centroid and others.