GTreeParticle: removed the "." at the end of the "particles" branch name
Modularized CMakeLists

Introduces lists for the common header and cc files and then uses those
in the executable targets. This makes it easier to add files to that are
common to all targets.
TreeTrigger: Added branches: mc_evt_id, mc_rnd_id for pluto MC true information matching.

These branches get filled with ID numbers then creating
pluto data (using the "split_pluto_events" program, for example).
Then they get passed through a2geant and acqu. Using these you can then
later check that the reconstructed events match with the events stored
in the pluto mc true tree when combining.
Added Pluto Tree
Added random ID to GPlutoTree.