SUSYTools: correction file loading for ElectronEfficiencyCorrectionTool to enable PLVTight

To enable PLVTight use:

• Made it possible to do correction file loading for ElectronEfficiencyCorrectionTool and override map file. Config file setting e.g.
  Ele.EffCorrFNList: PLVTight:filepath.
• If configured, the specified correction files will be used for the tagged WP only, for regular and highPt iso SFs. Trigger SFs are untouched and use the map file as before (with fallback WP in case of PLV).

Additional edits:

• Small fixes to SUSYToolsTester.cxx and Jets.cxx for the nightly tests.
• Disable Ele Gradient Iso test in WP checker nightly test to speed up.

Reference files change.
The reference files are updated, so the test in the nightly will fail until this is merged.