allow multiple configs

[yarikoptic]

E.g. if we have "center-wide" one, and then per-dataset specific (btw -- what would be the logical location to keep it around under?), it would be cool if I could -c /path/center.cfg -c .validator.cfg $PWD or something like that. ATM second -c just overrides previous.

I guess it would be difficult if not impossible to "merge" configurations so most probably should be just processed in order to determine which messages (errors/warnings) could be not reported

Cheers!