2017-05-31 RecSys v21r4

This version uses Gaudi v28r2, LHCb v42r4 and Lbcom v20r4 (and LCG_88 with ROOT 6.08.06)

This version is released on 2017-patches branch.

Performance optimisations

[MR !571] TrackVectorFitter: process chunks in a more convenient way to avoid clone checking. Gains [1-5]% in speed for TVF depending on dataset.
Compared to TMF (approx values): magup2016: -18%, upgrade-baseline: -2%.
to_process is populated with chunks of size BatchSize.
BatchSize is defaulted to 50 after parameter exploration.
Population of nodes in TVF casts smooth state vector only once (very small gain).

Bug fixes

[MR !582] PrFitPolinomial.cpp: fixed small compilation warning that could have lead to memory corruption

Monitoring changes

[MR !599] Add per panel Cherenkov resolution plots
[MR !578] Use force=True when PrintOn/PrintOff combination is used
PrintOff() following PrintOn() does not always restore print level as, per default, PrintOn() will not decrease LogFilter.printing_level if it is already 0. However, PrintOff() will increase it unconditionally. The fix (without touching Gaudi) is to use PrintOn(force=True).
Also removed some lone PrintOff()s.
[MR !564] Add a header in PrChecker and PrChecker2 printout
This makes it possible to (sensibly) use a findReferenceBlock() validator. Right now there is no proper signature line as the first line contains performance numbers that might change.