Jdk classes no longer 'created', stopped 2nd registration of empty classes

- Apparently, ZC tried to create (empty) java.lang and java.util classes
- Script blocks and Module Highleveldefinitions create the same class and they aren't merged but the scripts blocks (which run later) try to replace the definitions. Workaround by preventing 2nd registrations and printing to System.err

JavaBytecodeCompiler/src/main/java/org/openzen/zenscript/javabytecode/JavaBytecodeModule.java

 	public void addClass(String name, byte[] bytecode) {
 		if (bytecode == null)
 			return;
-		
-		classes.put(name, bytecode);
+
+		if(name.startsWith("java")) {
+			System.err.println("Invalid name " + name);
+		} else {
+			classes.put(name, bytecode);
+		}
 	}
 	
 	public void addScript(JavaScriptMethod method) {

JavaBytecodeCompiler/src/main/java/org/openzen/zenscript/javabytecode/JavaCompiler.java

 				target.addScript(method);
 
 			entry.getValue().classWriter.visitEnd();
-			target.addClass(entry.getKey(), entry.getValue().classWriter.toByteArray());
+
+			if (target.getClasses().containsKey(entry.getKey())) {
+				//TODO Scripts and definitions seem to create the same class. Bad!
+				System.err.println("Trying to register " + entry.getKey() + " a 2nd time");
+			}else{
+				target.addClass(entry.getKey(), entry.getValue().classWriter.toByteArray());
+			}
 		}
 
 		return target;