allow cross-reference retrieval for loci from ensembl to Uniparc and other databases

EnsemblProtists and other databases often have cross-references for their protien coding regions to other databases than Uniprot, but there are still rich sets of 'predicted' annotation for those proteins. See e.g.
Tb927.3.1990 -> http://protists.ensembl.org/Trypanosoma_brucei/Transcript/Domains?db=core;g=Tb927.3.1990;r=3:516029-526283;t=AAZ10234

In jalview, the gene + transcript are returned, but since these have Uniparc entries rather than Uniprot, they do not get a 'show cross-references' option under 'Calculations'.