add gas-specific TRT monitoring histos
Add physics validation histograms to detect variations in the number of TRT hits and hight threshold TRT hits separately for Xenon and Argon straws, as well as histograms with mu dependence that can be used for tunings. Checked histograms are filled correctly. Tagging @cgrefe, @beddall, @jchapman, @gcallea and @dhayden
Edited by John Derek Chapman