Add filter option to TQFolder delete command

Release notes

Add filter to TQFolder $delete() command (to delete only TQSamples or TQSampleFolders)

Details

The command can e.g. look as follows: $delete(bkg/?/c16a/top/ttbar/?!, filter=sf). This, e.g., could delete all the TQSampleFolders inside bkg/?/c16a/top/ttbar but not the .cutflow and .histograms TQFolders and such provides an easy method to trim the SF (e.g. during merging). There is also a skipsilent option that can be set to true, in order to prevent lots of errors to be printed that are harmless anyway.