Do we need the sequences table?

[childers]

After loading hundreds of BLAST databases, our sequences table is getting really, really big.

I think the only reason the sequences table exists is for doing lookup to get the sequence form the input fasta file.

With BLAST+, the blastdbcmd program can return a sequence from the ID, removing the need for the table, and the extra steps on setting up a new database.

What functions use the sequences table?
Can these functions be refactored to use existing BLAST apps, or simplified?

[hsiaoyi0504]

@childers I think this can be closed, right ? It's been duplicate in #288.