WIP: Matt dv slim mods

This hasn't been tested yet but should now apply our preselection at the DV level (or at least very close to it). We should also continue to apply our existing preselection offline in the pipeline. This slimmed version writes out only a subset of the branches (this can probably be honed). In particular we don't need the Isolation branches as they are never used but we should make sure we are not missing branches we need or indeed that we don't have an excessive number of branches we don't use.