Reduce inefficiency in use of whole-genome alignments

[TBradley27]

At the moment, in order to generate multiple sequence alignments for each 3' UTR, FilTar downloads entire whole genome alignments and then extracts the relevant genomic co-ordinates (using the transcript co-ordinates of a reference species).

This is extremely inefficient and costly. FilTar should instead download MSAs on a UTR-by-UTR basis by more cleverly interacting with the UCSC server.