Changed adding nodes with the CaseRule button to select the parent (to
allow multiple cases to be made without manually reselecting the parent
node), as well as temporarily enabling the AddNode button as a
FinalizeCaseRule button (to select the node recently created).
FinalizeCaseRule still needs to be modified to autodetect the relevant
CaseRule and set it as the justification for the node it creates.

Also fixed a bug with justificationApplied messages not being sent when
a justification is applied (which was interfering with the temporary
enabling of AddNode/FinalizeCaseRule).