Memory query class & Removal of RT/MZ metavalues

new class SYSTEM/SysInfo which allow to query  memory usage of current process (needs testing on MacOS; linux & windows seems to run fine)

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.