Draft: Adding a new D2AOD format to allow command-line skimming of PHYSLITE

This MR adds a new D2AOD format (D2AOD_SKIM) to the derivation framework to allow users to skim PHYSLITE via the command line, rather than the current situation where they must set up their own formats. Usage is:

Derivation_tf.py --CA --inputDAOD_PHYSLITEFile DAOD_PHYSLITE.33081115._000042.pool.root.1 --outputD2AODFile test.pool.root --formats SKIM --skimmingExpression "count(AnalysisMuons.pt > (1 * GeV)) >= 1" --skimmingContainers xAOD::MuonContainer/AnalysisMuons

The last argument should be a list of all containers touched by the skiming expression. The skimming string itself is the usual ExpressionEvaluation string, so identical to the strings used in the derivation framework. Per-event content should be identical to PHYSLITE.

This would not be used in official production due to the generic format name. In cases where official production of a PHYSLITE skim were needed, one would need to define a new format as ususal. This could, however, be the basis of a user skimming service, if we decide to have such a thing in the future.

In addition this creates a new subcategory of common flags with the domain Derivation