refactored the logic package class. in specific:
1.in CommandExecutor, modified constructor, added accessor methods. refactored out the error message and put them in separate class called ErrorMessages
2. in logicfacade class, refactored enum to another separate class called Action. Also added getListMethod to return list to the GUI
3. added CommandType.java which contains the different command type . i.e: add, delete etc. This is to make it more OOP
1. in Action.java, changed the accessor to public access
2. in CommandType, changed the class to public class
3. added a Junit test for the class Action. all test cases passed.
apply good naming practice to some variable names. added comments for ErrorMessages class