RICH Future : Fix build platform differences.

A number of fixes to address some differences seen between the opt and dbg builds in the nightly tests.

1. I now truncate the Cherenkov theta and phi precision to 7 d.p. More than enough physics wise, but removes noise due to small instabilities due to opt using -O3 and dbg not.
2. Update a number of MC monitors to properly handle situations where a Track object has multiple possible MCParticles associated to it. Works around issues due to Relations sorting not being stable. (Relies on LHCb!592 (merged)).

The rest of the changes is just some additional debug here and there, added along the way.