No detection of failed enrichment in deconv

[Clockwork-Rat]

when passed a failed enrichment, deconv tries to deconvolve the "failedEnrichment.txt", should produce and error or warning

[jtladner]

Instead of specifically ignoring "failedEnrichment.txt", let's add a flag for the user to specify what string is expected at the end of each file containing enriched peptides. By default, this string should be "_enriched.txt".