Fix boolean flags defaulting to false.

PlotSquared/src/main/java/com/intellectualcrafters/plot/flag/FlagValue.java

@@ -48,12 +48,24 @@ public abstract class FlagValue<T> {
 
         @Override
         public Boolean parse(final String t) {
-            try {
+            switch (t.toLowerCase()) {
-                return Boolean.parseBoolean(t);
+                case "1":
-            } catch (final IllegalArgumentException e) {
+                case "yes":
+                case "allow":
+                case "true": {
+                    return true;
+                }
+                case "0":
+                case "no":
+                case "deny":
+                case "false": {
+                    return false;
+                }
+                default: {
                     return null;
                 }
             }
+        }
 
         @Override
         public String getDescription() {