MET TST Systematics Pre-Recs

This MR updates the default paths of the METSystematicTool to point to the ones of the R22 pre-recommendations. In addition, two adjustments from R21 are propagated:

1. adding a protection for events where no object is added to the MET calculation and the MET consistent of only the soft term
2. adjust the MET TST systematic name to the __1up and __1down scheme

Tagging @hpacey, @aoneill & @gotero.

Reconstruction/MET/METInterface/METInterface/IMETSystematicsTool.h

@@ -25,22 +25,22 @@
 namespace met {
 
   namespace softCaloAffSyst {
-    const static CP::SystematicVariation MET_SoftCalo_ScaleUp  ("MET_SoftCalo_ScaleUp"  );
-    const static CP::SystematicVariation MET_SoftCalo_ScaleDown("MET_SoftCalo_ScaleDown");
+    const static CP::SystematicVariation MET_SoftCalo_ScaleUp  ("MET_SoftCalo_Scale__1up"  );
+    const static CP::SystematicVariation MET_SoftCalo_ScaleDown("MET_SoftCalo_Scale__1down");
     const static CP::SystematicVariation MET_SoftCalo_Reso     ("MET_SoftCalo_Reso");
   }
 
   namespace softTrkAffSyst {
-    const static CP::SystematicVariation MET_SoftTrk_ScaleUp  ("MET_SoftTrk_ScaleUp"  );
-    const static CP::SystematicVariation MET_SoftTrk_ScaleDown("MET_SoftTrk_ScaleDown");
+    const static CP::SystematicVariation MET_SoftTrk_ScaleUp  ("MET_SoftTrk_Scale__1up"  );
+    const static CP::SystematicVariation MET_SoftTrk_ScaleDown("MET_SoftTrk_Scale__1down");
     const static CP::SystematicVariation MET_SoftTrk_ResoPara ("MET_SoftTrk_ResoPara" );
     const static CP::SystematicVariation MET_SoftTrk_ResoPerp ("MET_SoftTrk_ResoPerp" );
     const static CP::SystematicVariation MET_SoftTrk_ResoCorr ("MET_SoftTrk_ResoCorr" );
   }
 
   namespace jetTrkAffSyst {
-    const static CP::SystematicVariation MET_JetTrk_ScaleUp   ("MET_JetTrk_ScaleUp"  );
-    const static CP::SystematicVariation MET_JetTrk_ScaleDown ("MET_JetTrk_ScaleDown");
+    const static CP::SystematicVariation MET_JetTrk_ScaleUp   ("MET_JetTrk_Scale__1up"  );
+    const static CP::SystematicVariation MET_JetTrk_ScaleDown ("MET_JetTrk_Scale__1down");
   }
 
   enum SystType {