Versioning - Backwards Compatibility #49

For everyone to now:

SolidPython2 does not follow regular semantic versioning.

Instead:

• the major version is always 2
• minor version bumps (might) include backwards incompatible changes (api changes)
• everything else are "patch version" releases

-> v.2.1.0 includes backwards incompatible changes, especially the parameter order of the cylinder primitive.