Compara self-alignments

http://staging.ensembl.org/info/genome/compara/analyses.html doesn't show human-vs-human any more.
This is because we now compute this alignment in-house instead of importing it from UCSC.

The code that generates the list assumes that only UCSC self-alignments are allowed, and this commits fixes that assumption.

NB: I haven't tried it on my sandbox. I could do it later today / tomorrow as I have to test another change anyway