cubicweb-trackervcs #2518844 another checkin message to link a ticket to a cs, without closing it. [validation pending]

ie similar to "closes". "get ahead" ?

prioritynormal
typeenhancement
done in1.1.0
load0.100
load left0.000
closed by#baad831685da [hooks] add a "related to #xxx" keyword
patch[hooks] add a "related to #xxx" keyword [applied]