Addlw instruction (#4)

* Added addlw command

* Write to program list

* Included CommandUtils as helpter class. Sorted classes into packages

* Revert changes on HelloWorld

* Revert "Revert changes on HelloWorld"

This reverts commit a08a336864fb2aa2bbc5a4e37ca360765774965e.

* Added example execution of Addlw command

commands/Command.java

@@ -0,0 +1,6 @@
+package commands;
+
+public interface Command
+{
+    void execute();
+}