changes number parsing to use BigDecimal as the backing type

* updated tests to support BigDecimal as the backing type for numbers
* updated some test resource handling to java7 try-with-resources format
* cleaned up some other minor compiler warnings

src/test/java/org/json/junit/data/MyEnumClass.java

@@ -8,13 +8,13 @@ public class MyEnumClass {
     private MyEnumField myEnumField;
 
     public MyEnum getMyEnum() {
-        return myEnum;
+        return this.myEnum;
     }
     public void setMyEnum(MyEnum myEnum) {
         this.myEnum = myEnum;
     }
     public MyEnumField getMyEnumField() {
-        return myEnumField;
+        return this.myEnumField;
     }
     public void setMyEnumField(MyEnumField myEnumField) {
         this.myEnumField = myEnumField;