New plugin to store trigger results has been added

The size of PEC files produced for a RelVal ttbar using the new SlimTriggerResults plugin has decreased by about 50% compared to the old TriggerResults plugin. The improvement is expected to be even more pronounced with real data.
A little optimisation in calculation of trigger states
A bug in SlimTriggerResults has been fixed

The plugin used to fill the output tree with all visited events, even if the filter mode is activated and some of the events are rejected.:
Added fillDescriptions method

Description on how this method is used is available in [1].
[1] https://twiki.cern.ch/twiki/bin/view/CMSPublic/SWGuideConfigurationValidationAndHelp
General description of the plugin has been adeed