Issue 624 nonmodifiable contradiction (#649)

* Update TreeView.java

Made board unmodifiable when a selected tree node is part of a contradiction branch

* Added contradiction check to mouse event

Removed previous changes from TreeView

Added board modifiability update to TreeController for each mouse press on the proof tree: modifiability is determined by whether or not the current selected node is part of a contradiction branch

* Added comments

Added comments to TreeController

* Updated modifiability on rule application

Set board modifiability of the current transition to false when a contradiction is applied in ValidateContradictionRuleCommand;
Removed previous change to TreeController.

src/main/java/edu/rpi/legup/controller/TreeController.java

@@ -2,6 +2,7 @@
 
 import edu.rpi.legup.model.Puzzle;
 import edu.rpi.legup.model.tree.Tree;
+import edu.rpi.legup.model.tree.TreeElementType;
 import edu.rpi.legup.ui.boardview.BoardView;
 import edu.rpi.legup.ui.proofeditorui.treeview.*;
 
@@ -42,7 +43,7 @@ public void mousePressed(MouseEvent e) {
 
     /**
      * Mouse Released event sets the cursor back to the default cursor and reset info for panning
-     *
+     * Set board modifiability
      * @param e MouseEvent object
      */
     @Override

src/main/java/edu/rpi/legup/history/ValidateContradictionRuleCommand.java

@@ -66,9 +66,11 @@ public void executeCommand() {
             if (transition == null) {
                 transition = tree.addNewTransition(treeNode);
                 transition.setRule(newRule);
+                transition.getBoard().setModifiable(false);
                 tree.addTreeElement(transition);
             }
             else {
+                transition.getBoard().setModifiable(false);
                 tree.addTreeElement(treeNode, transition);
             }