o.c.graphene.opiwidgets: value context menu activated for line graph
o.c.graphene.opiwidgets: moving context menu logic in superclasses
o.c.graphene.opiwidgets: scatter graph review, popup menu for value
o.c.graphene.opiwidgets: bubble plot review; popup menu for value
Merge branch '3.2.x' of git@github.com:ControlSystemStudio/cs-studio.git into 3.2.x