Updated swig wrappers.

Wrappers now include:
- Support for STL vectors.
- Automatic removal of units
- Automatic conversion of numpy arrays to lists
- Addition of units to output parameters
- Proper handling of OUTPUT reference parameters
Restructured test
Replaced with stripUnits with one from simtk.openmm
Add missing import of simtk.unit
Merge pull request #9 from jlmaccal/master

Updated swig wrappers.
Merge branch 'upstream'

Conflicts:
	python/exampleplugin.i
Use stripUnits from main openmm public interface.