Fix pepID metavalue usage

separated/squashed commits

Removal of RT/MZ meta values from PeptideIdentification and replacement with members.
Access should be much faster.
Memory benchmark shows 10% less memory consumption on Windows (840 -> 740 MB for 190 MB idXML file). This is still way too much, but we have a plan for optimizing the rest.

cccd4a1 should be removed for release 1.12 -- I'll open a ticket.