Add functional charged-particle maker algorithm
A Gaudi::Functional algorithm to make (charged) LHCb::Particle objects.
Apart from being functional, this differs from the usual CombinedParticleMaker in that it uses LoKi to apply cuts to the input ProtoParticle objects and to the associated Track objects (IMO it would be nicer to separate out these two filters). It does basically the same things as NoPIDsParticleMaker and CombinedParticleMaker; I tried to support the superset of functionality.
I wrote this for the HLT2 prototype. It's not strictly necessary for that (I only realized this later...), but it's written now so I thought I'd add it to Phys. I don't expect it to last very long as LHCb::Particle will probably look very different soon.