groupGenes doesn't support TCR data

[Jason Vander Heiden]

Looks like everything is hardcode to IGH, IGL and IGK. The code should work for TCR data as well (TRB, TRD, TRA, TRG).

This impacts scoper and shazam functions that are dependent upon `groupGenes`.

The only_igh argument should probably be changed accordingly, so as not to be confusing. only_heavy would be better - still wrong, but less wrong.

[nima nouri]

Resolved by eaffd01