OMF: refactoring with breaking changes

- parameters for rotamers are derived from PDB structures by ourselves
- removed LOSSY and INFER_POSITIONS options. User can now just give a
  max error and OMF will figure out by itself the best strategy.
- Increased accuracy by storing angle differences in rotamer compression.
  That means: instead of blindly using the angles from the derived parameters,
  we sacrifice 4 bits to store differences to that optimal angle.
- CANNOT LOAD OMF FILES FROM PREVIOUS VERSIONS ANYMORE