define IRC notification commands for wikidata

this defines new notification commands, copied
from the existing IRC notification commands that
make icinga-wm work, but for wikidata

notify-host-by-irc-wikidata
notify-service-by-irc-wikidata

these will be used by a new contact "irc-wikidata"
which i created in the private repo already

and this should enabled us to make icinga-wm join
#wikidata as a second channel but NOT spam them with
all notifications but only those they care about
(currently just the wikidata dispatch check)

Bug: 65291

Change-Id: I465f13431360b54c5c3f8c1216cecfa8bc2792d9
Merge "define IRC notification commands for wikidata" into production