More config block fixes

1. As discussed on MatterMost, the overlap removal selection is flagged on ConfigAccumulator in a way that is inconsistent with all other selections, i.e. with the containerName including _%SYS%. This removes the systematics suffix. @krumnack did you come to any conclusion on whether this is needed? It made my analysis code more consistent, and seems to work as intended.
2. The JVT selection decoration expression should include as_char to be read correctly when accessed with the alias.
3. The ConfigAccumulator.addPrivateTool() argument names were misleading, so now made to agree with what the args actually do.
4. Discussed with @jburzyns, set the number of tracks required for vertex counting to 2
5. Permit configuration of the flags used for event cleaning, for example to use the 'DFCommonJets_isBadBatman' flag in addition to loose jet cleaning (relevant for data15/16)

One question I have for @krumnack, @tadej, @mleblanc, @camacho perhaps is:

• Do we want the fJVT selection to be associated with the string 'jvt' as is currently done (see 'JetAnalysisConfig.py:L239') or should it be 'fjvt'? The former I think means you would ask for all jets passing either JVT or fJVT with one decoration, while the latter means you would have to check two.