Draft: Duplicates removal in SelectionFromWeightedRelationTable

Remove duplicated particles from "SelectionFromWeightedRelationTable". Dubugging, I realised that duplicates of particles in LHCb::Particle::Selection may appear if the relation-table is built including different particles as reference (eg. using F.GET_ALL_BASICS()) or in the case of multiple candidates per event (quite common for D*->D0pi decays). This will used in charm/isolation.py for the charm WG (see Moore!2420 (merged)), for the percistency of tracks for isolation variables.

Depends on !3434 (merged), !3444 (merged) and on !3441 (merged)

To be tested with Analysis!1028 (closed) and Moore!2748 (closed).

In addition:

• WeightedRelationTable(.cpp) changes its name in RelationTable(.cpp)
• SelectionFromWeightedRelationTable changes its name in SelectionFromRelationTable