It's now difficult to get pfam full alignments

[jamesmkrieger]

Only seed alignments are available together with the families. To access full alignments, we need to download the a big gz file containing all of them together from the full release from ftp e.g. https://ftp.ebi.ac.uk/pub/databases/Pfam/releases/Pfam37.0/ and query it.

For now, I have made seed the default in #1858, but we will also need new code similar to what we have for pdb clusters.