Changes to caserule so that it can make branches by clicking on the
board, without allowing arbitrary rule branches. Incomplete.
Added return values for addJustification.
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).
Fixed FinalizeCaseRule button so that it's now enabled or disabled based
on selection changes. Fixed FinalizeCaseRule button so that it now
correctly autodetects the CaseRule used for the previous cases. Still an
image bug (not appearing) for the CaseRules.
Attempting to modify a non-transition (circle) that already has a
basic-rule child now does nothing instead of modifying said child.
Merge branch 'CaseRule'

Conflicts:
	code/edu/rpi/phil/legup/newgui/CasePanel.java
	code/edu/rpi/phil/legup/newgui/Tree.java