Cleanup selmatt

Drop SusyAnaDefsMatt, SusySelectionMatt that were introduced when pulling in the fake procedure.
Now only use SusySelection, and define the few extra functions we need in MeasureFakeRate2.
There are still a few things that will be dropped: counters, see 5afb14f64d222b5f4761be5b00bcaa8dc83ea450 and aef63184fbb0d961dcc8574faf394a54631908ee), and getEvtWeight (see 3545ff64800bc21334c8186f7c00a80b9098137b), but most of the confusing stuff is cleaned up.
Verified on PowhegPythia8_AU2CT10_WZ_W15Z15_mll3p804d0_2L5 that the histograms produced by measureFakeRate have still the same contents.
Also the counters are still the same, with the exception of the trigger counters, which anyway were wrong (see fdeb4bdabc8228977c68e34338e86059ad9c1668)