TrigCost: Save L1 rates

• create L1 triggers' rates table
• update root directory structure to be compatible with the website (to be approved)

Triggers
    L1 and HLT triggers
Globals
    Global groups

to

All
   Rate_ChainL1_HLT
         L1 triggers
   Rate_ChainHLT_HLT
         HLT triggers
   Rate_Group_HLT
         group triggers

• add labels to data histogram

example with linked histograms based on AOD input from test_trigP1_v1PhysP1_T0MonTrf_build test : https://atlas-trig-cost.cern.ch/?dir=aporeba&type=&tag=rate-prediction-ATR-12345-TriggerValidation-prescale&run=000001&range=All

Tagging @tamartin @mark