Allow addition of sequences that aren't the same length as others within that locus file

[djlohman]

Remove the prohibition on importing sequence files in which the sequences have different lengths (usually because they are not aligned). This would allow adding new taxa with multiple loci simultaneously. Currently when this happens, the warning is:

Some sequences in the taxonset Danaus_COI_FullTaxon weren't added. These are:
“Dgenutia BB52 Maluku: It is too short (1212 bp, while the column is supposed to be 1246 bp)”

I would change this to:
Some sequences in the taxonset Danaus_COI_FullTaxon differ in length from other sequences for that locus. This suggests the locus should be realigned. Use with caution. These loci of differing length are:
“Dgenutia BB52 Maluku: It is too short (1212 bp, while the column is supposed to be 1246 bp)”