cubicweb-condor #2962957 de-hardcode the reference to the 'managers' group [validation pending]

Allowing dependant cubes to specify which groups really can do managerial stuff.

prioritynormal
typebug
done in1.0.0
load0.100
load left0.000
closed by#7dd35845c675 [views] do not hardcode refs to the managers group to allow easy override (closes #2962957)
patch[views] do not hardcode refs to the managers group to allow easy override (closes #2962957) [applied]