VeloRecMonitors: Merge branch 'shanzhen-VeloOfflineDQMonitor' into '2016-patches'

Add plots for VELO offline DQ monitoring

A few new plots were added to VeloClusterMonitor class, for Offline VELO DQ monitoring purpose. Old VeloClusterMonitor class was also cleaned up. New plots are protected with an option that by default it switched off to prevent Brunel calling it, and switched on only in Vetra for offline DQ monitoring.

See merge request !80 (merged)