Fixed Nurikabe Rules Printing Duplicate Error Messages (#526)

* set test points to make sure the STT files are loaded in correctly

* testing transitions

* added a test case, BlockInVerticalPath for LightUp that tests there isn't a contradiction if there is a block between two bulbs.

* added a test case, CannontFillMiddle for LightUp that tests CannotLightACell Contradiction Rule

* removed unnecessary indent

* Added unit tests tor CannotLightACellContradictionRuleTest and TooFewBulbsContradictionRuleTest.

* Added test LightUp files for testing

* removed an unnecessary comment and spacing

* Added another set of tests for TooManyBulbsContradictionRule

* Added Randomly Generated 7x7 lightup puzzles

* prevented the same error message from being created numerous times when checking for direct rules.

src/main/java/edu/rpi/legup/puzzle/nurikabe/NurikabeBoard.java

@@ -15,6 +15,10 @@ public NurikabeBoard(int size) {
 
     @Override
     public NurikabeCell getCell(int x, int y) {
+        if (y * dimension.width + x >= puzzleElements.size() || x >= dimension.width ||
+                y >= dimension.height || x < 0 || y < 0) {
+            return null;
+        }
         return (NurikabeCell) super.getCell(x, y);
     }