RICH - Minor optimisation

Various small optimisations. Most notable being :-

1. Add to reco base class methods to retrieve list of active mass hypotheses excluding the below threshold type. This type needs to be treated differently in a number of places, and often is just skipped. This removes the need for a if block to do that skipping in a number of places.
2. Remove unnecessary normalisation of final photon direction in quartic reconstruction.
3. Remove some residual aerogel support code.

Note point 1. above means some minor perturbations in the Brunel qm test logs is likely (due to the fact in one place an incorrect comparison to the below threshold type was being performed).