Hetatms are potentially skipped but if they come with an ANISOU record,
ost expects them to be there. As a solution we simply increase the
permissiveness as we already do it when having the calpha_only option
active.

* Added actions interface including one action to compare structures (meant to
  replace use of molck/lddt-binaries and make QS-scoring accessible)
* Added single chain lDDT scores using QS chain mapping and weighted average
* Added penalties for extra chains (ref and mdl) for oligo lDDT scores

Combination of reference_existing_object and RemoveChain can lead to segfaults.
Overhead of change is 1us per call for a test case with 18 chains. Hence it is
absolutely negligible.