Change value of FlowElement float variable to a more convenient format

This MR changes a float value stored on charged FlowElement from a ratio to an absolute value. This will significantly simplify its usage at AOD level for clients. To facilitate this the minimal intervention was to add an extra float to the internal eflowRec EDM only used in Tier0 reco. I also included a bug fix to the physics validation configuration for FlowElements such that it would now work again after recent MR related to FlowElements and PFO. A WARNING was also removed about an invalid PFO ReadHandle in physics validation code (this is expected and the ReadHandle is not used anymore). This will remove pollution from the log files. A future MR will address fully removing usage of the no-longer supported PFO from physics validation. For testing I ran: RunTier0Tests.py - no new crash, warning or error. Output changes of course. Ran on 2000 ttbar events and verified standard physics validation plots do not change at all (the variable I changed in the output is not monitored). Ran extensive detailed tests to verify the new variable format behaves as expected.