Simplified database download

When inputting a database, there are three options:

1. input one of three reserved values: uniprot, swissprot or taxids
2. input a FASTA database
3. input a DIAMOND formatted database

UPIMAPI will first check if the DIAMOND version of the databases exist, and if it finds it, will run annotation with it.

1. in --resources-directory folder, either uniprot.dmnd, uniprot_sprot.dmnd or taxids_database.dmnd
2. the database filename with termination replaced with .dmnd
3. the database filename itself

If that doesn't exist, UPIMAPI will search for the FASTA format, and if it finds it, will convert to DIAMOND format.

1. in --resources-directory folder, either uniprot.fasta, uniprot_sprot.fasta or taxids_database.fasta
2. the database filename itself
3. will exit with file not found error

This removes the need to tinker with the --skip-db-check parameter, but more trust is placed on the user.