Various changes associated with issue #204 (closed).
- Reduced code duplication for handling prostar conversion and IO
- Simple conversion to/from AVL/FIRE geometries
- New library basis for conversion to/from CCM geometries - handles multiple regions, conformal interfaces etc. No support for film or 2d shell geometries
- Improved infrastructure for writing VTK content. Will propagate usage through other parts of the code in the future.