BaseWindow: break circular references through actions
BaseWindow: break circular references through actions

PyGObject is unable to trace through GtkActionGroup and GtkUIManager
to find the action objects where we've connected signals, so we need
to explicitly break the cycle by dropping the references we hold to
the GtkActionGroup and GtkUIManager.

alexey4petrov/reinteract,alexey4petrov/reinteract,alexey4petrov/reinteract