Philosopher failed to mark contaminant human proteins with prefix `contam_`

[fcyu]

This is a bug reported by emails. I put it here in case we forget it. It also let potential affected users know: human contaminant proteins are always not marked with prefix contam_ even when the original fasta file is not from human proteome.

Following are the steps to reproduce this bug:

1. generate a test.fasta file with entry

>sp|OABCD|Test_A Keratin, type I cytoskeletal 15 OS=Ovis aries GN=KRT15 PE=2 SV=1
TESTABCD

2. Run Philosopher command

philosopher.exe workspace --clean
philosopher.exe workspace --init
philosopher.exe database --custom test.fasta --contam --contamprefix --nodecoys
philosopher.exe workspace --clean

Following are the test.fasta and the output from Philosopher as references. dev.zip

Best,

Fengchao