Fixes #20, so that OpenSCAD’s use() and include() functions still work, even if you don’t import SolidPython as ‘form solid import *’
Fixes #21.  SolidPython now passes any extra arguments on to OpenSCAD.
Added tests for include, use, and passing extra arguments to OpenSCAD.  Fixed a bug that meant that include() has never (!) worked.
Merge branch 'feature/Accept_extra_args_to_SCAD_module_GH_#21' into develop
Merge branch 'feature/scad_import_without_python_star_import' into develop

Conflicts:
	solid/solidpython.py
committing merge?  Thought I just did this.