Option to add tags a runs

[vincentvanhees]

Hi Jairo, the repository looks great. I used it today and it was very helpful.
One possible enhancement could be that we allow the user to add a tag to each run.

For example:
output_230725_111328_MasterBranch
output_230726_111328_PossibleFixIssue23
output_230727_111328_GGIR2.9-5
output_230728_111328_GGIR2.8-3

In that way it becomes a bit easier to remember how runs differed.

The implementation could be:

• Add argument 'tag' to runPipeline (default = NULL)
• Inside runPipeline strip tag from all underscores, e.g. master_branch would become masterbranch.
• If tag is specified then add "_tag" to the folder name
• Ignore the _tag part from the folder name when comparing results.