Add ROS Monitor class in TrigCostAnalysis

Add ROS Monitor class to keep track of ROB requests and create histograms. Data is filled based on values from HLT_TrigCostROSContainer saved in CostData.

Also:

• use ROBDataMonitorStruct to pass information to Cost. Associated with request ROBDataStructs are stored inside, as well as the elapsed time (as timestamps)
• add more details to store in EDM: lvl1ID, start and 'stop - timestamp of request execution and list of ROBDataStruct values

In follow up MRs:

• use rob2ros mapping in MonitorROS and CounterROS
• refactor ROBDataStruct to store just a single word
• add and fill necessary histograms in CounterROS::newEvent
• save data to csv in trigCostHistToCSV.cxx

Example histograms:

• ROBSize_perCall size.pdf
• ROBHistory_perCall history.pdf

Tagging @mark @tamartin