refactor test classes to their own modules

MyBigNumberBean.java

@@ -0,0 +1,11 @@
+package org.json.junit;
+
+import java.math.*;
+
+/**
+ * Used in testing when a Bean containing big numbers is needed
+ */
+interface MyBigNumberBean {
+    public BigInteger getBigInteger();
+    public BigDecimal getBigDecimal();
+}