Allow a placeholder for main FHiCL configuration name in output files (RootOutput, TFileService)

[knoepfel]

This issue has been migrated from https://cdcvs.fnal.gov/redmine/issues/22357 (FNAL account required)
Originally created by @PetrilloAtWork on 2019-04-12 00:04:06

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I would like to be able to specify an output file name for, e.g., RootOutput module, like:

filename: "%c_%p-%tc.root"

that replaces the first token (%c in the example) with the basename of the configuration file, so that e.g.

art -c ./job/generateBeautifulEvents.fcl -n 10

would produce files like generateBeautifulEvents_Gen-20190402T170247.root.