112x comb2021 chcomp

[amarini]

Extend Channel compatibility to have slightly more flexibility in mapping POIs name.

example of syntax:
-g ch1_ch:r_ggH [ -g ... ]

At the moment grouping is restricted to part of the channel name

To port to: 112x-comb2022 and 112x

[amarini]

Check interplay w/ #760.
Probably it would be good to rewrite part of this to mimic multisignal process, in the master.