Fixes for Truth derivations in master
Three fixes to get truth derivations running in master.
First, change the import of the EventDensity algorithm, which had been fixed for the new config but not for the old config.
Second, turn off geometry loading when running truth derivations (it isn't needed, and brings in a bunch of tools that also aren't needed).
Third, make sure that when a MET configuration is requested, if it's a truth configuration it doesn't set up a bunch of track extrapolation tools (which as far as I know, are not needed for such configurations). If the suffix is something other than 'Truth' here (which should only be the vanilla truth MET), then the tools are still loaded, which should allow people to construct whatever slightly weird things they might want.