remove eg candidates from PU calculation, via richard-cms

The eg candidates were intially part of the PU calculation to be used for a region-calibration scheme which was abandoned. Clean up the PU code to no longer need egcands and to simplify the logic.
fix floating/fixed point math in PU subtraction, via richard-cms
guarantee that Stage 1 obeys scale limits, via richard-cms
fix possible array-out-of-bounds in PUM0 calculation, from richard-cms
Merged l1t-bugfix-algbugfixes-CMSSW_7_2_X from repository cms-l1t-offline
Fix GMT input tag for simGtDigis, from apana
Fix bug in scale check from MHT
Merge pull request #5686 from cms-l1t-offline/l1t-bugfix-algbugfixes-CMSSW_7_2_X

L1t bugfix algbugfixes cmssw 7 2 x