Latest N-lumiblocks plots for online monitoring
This adds one major new feature. For plots which are y_vs_lb, it will make plots which always show the last N lumiblocks on the x axis. An example usage would be:
group.defineHistogram('LB,y', type='TProfile', opt='kLive=12')
While I was working on it, I noticed that there were two tests of the histogram providers doing approximately the same thing, so I combined these tests under one roof in HistogramProviderTestSuite.
This MR resolves ATLASDQ-685.