Updated MultiParticleFilter

This is in a bit of a hurry because we'd like to make a new signal request with these filters ASAP for some upgrade studies - thanks for your patience and help!

The MR extends the MultiParticleFilter to allow minimum eta values and phi ranges, as well as to include a generic selection for BSM particles. It has been validated in a few models and behaves as expected. I also include a new filter configuration based around the eta and phi slices currently available in HTTSim.

I'm marking squash commits to get rid of some gross dev stuff ...