Add IOVDbSvcConfig.blockFolder

Add a convenience method to IOVDbSvcConfig to remove database folders from IOVDbSvc.Folders and CondInputLoader.Load. Use it in Calorimeter/CaloLocalHadCalib instead of the hacky version there. This is useful for calibration jobs or calibration-testing jobs where one particular conditions is either read from an external file or produced in the same job.

The blockFolder method acts on a final ComponentAccumulator. It is supposed to be use either as postExec or in the __main__ section just before cfg.run() : blockFolder(cfg,"/TRT/Calib/T0")

Note that the folder-name matching is done with a simple string-find (no fancy regex), so it might block more than what you think. A warning is printed if more than one folder gets removed.

cc @serodrig who asked for this ...