ThOr functor clean-ups

Addresses a few rough edges found when rolling out ThOr functors to HLT2 lines:

• The PT functor now supports ParticleCombination inputs, allowing to act like the APT LoKi functor.
• The ETA, CHI2, and CHI2DOF GHOSTPROB, and MINIP functors now support LHCb::Particle input.
  • The CHI2DOF functor now works for both charged basic and composite objects, as the documentation states it should.
  • The TrChi2PerDoF implementation has been dropped as the CHI2DOF functor does the same thing.
• The MASS functor has been redefined to act like the COMPOSITEMASS functor, which has now been dropped. MASS now acts like the M and AM LoKi functors.
  • The original MASS functor has become the MASSWITHHYPOTHESES functor. This isn't used in HLT2 yet but will be useful as a WMASS equivalent once support is added.

To-dos

• A reasonable cut on the BPVLTIME functor removes all candidates; must be computing wrong.
  • Won't address here; see #204 (closed).

Required for Phys!945 (merged), Moore!862 (merged), DaVinci!550 (merged), and MooreAnalysis!39 (merged).