New version of pdbtorsions

pdbtorsions has been rewritten. It now correctly handles multiple chains and assigns the omega angle to the following residue instead of the preceding residue. The header format has also changed.

The old omega angle behaviour and the old header format can be obtained by using the -o flag or by naming the executable 'torsions' instead of 'pdbtorsions'.

The -m option (provided specifically for one application) has now been dropped.