Uniprot sourcename fix

[bsantan]

• Fix in merge.yaml to look in uniprot_genome_features for transformed files
• Fix in uniprot.py to us Uniprot prefix in protein IDs rather than uniprot_genome_features prefix

[hrshdhgd]

Instead of hardcoding strings I'd recommend using constants.py to declare as a variable first and then use it in the project

[bsantan]

I added constants to the uniprot.py file rather than strings.