Please add backbone selection to compute_lrmsd_pdb2sql()

[DarioMarzella]

Is your feature request related to a problem? Please describe. I would be able to calculate l-RMSD on different atoms of the backbone: only CA, or [CA, C, O, N] or [CA, CB, C, O, N], etc.

Describe the solution you'd like Allowing the user to give a list of atoms to be used for l-RMSD calculation as an optional parameter of compute_lrmsd_pdb2sql

Describe alternatives you've considered This might be appliable to irmsd as well.

[NicoRenaud]

The easiest solution is to pass the selection keyword of pdb2sql.get() down to the compute_lrmsd_pdb2sql() I'm not sure about the fast methods

[NicoRenaud]

first attempt in issue55 branch. we ca use

s.compute_lrmsd_pdb2sql(name=['CA','O'])
s.compute_lrmsd_fast(name=['CA','O'])

if the name kwarg is not specified it defaults to [C, CA, N, O]

[NicoRenaud]

need to be extended to irmsd (?) and cleaned up

[CunliangGeng]

Solved in PR #59