Document default values for minimum peptide/nucleotide lengths

Minimum length for a chain in the target structure
to be considered in chain mapping. The chain mapping algorithm first
performs an all vs. all pairwise sequence alignment to identify
"equal" chains within the target structure. We go for simple sequence
identity there. Short sequences can be problematic as they may
produce high sequence identity alignments by pure chance.

BUT: if you're scoring peptides or short nucleotides, you
really want to be able to reduce the default thresholds
(pep: 10, nuc: 4)

There are two use cases for this parameter: 1) decide whether a chain
mapping problem is actually solvable by naive enumeration and crash out if not
2) As a decision whether one should use naive enumeration or a heuristic
approach for chain mapping.

For the latter, n_max_naive meant the number of chains in the underlying
structure. Now its number of possible mappings for both cases.

requested by Andriy. Computes all IPS metrics on a per-interface basis

requested by Andriy. Computes all ICS metrics on a per-interface basis

enable contact scores and separate dockq and per-interface qs scores

Mainly for reporting in the compare-structures action
residues are reported as strings in format:
<cname>.<rnum>.<ins_code>, atoms are reported as
<cname>.<rnum>.<ins_code>.<aname>. This changes behaviour of
compare-structures and ost.mol.alg.stereochemistry
(ToJSON functions of violation info objects for the latter).

- Tell the user that biounit indices are 0-based
- More info in output on what chains are actually processed