[FEATURE] ProteinProphetAdapter

TPP PeptideProphet and ProteinProphet adapter. This version is working for XTandemAdapter idXML results. TPP/xinteract program will do the PeptideProphet analysis on the peptideID results and TPP/ProteinProphet will do the protein inference. 
Tests are added into the SEARCHENGINES folder.
I dont understand this comment, I dont think you can access "XTandem_score" if it is not registered as a meta value. So the check makes  a lot of sense to me and removing it sounds dangerous. Basically
`getMetaValue("XTandem_score")` should always be proceded by `it->metaValueExists("XTandem_score")`