Feat/display entity list (#100)
* Changed files to allow user interface ti display proper content during initialisation
* Fix checkstyle
* Update MESSAGE_USAGE of commands
* update Massage Usag for command
* Update UI to show CommandResult
* Fix checkstyle
* Morph User Interface to display entity list
* Change Entity list displayed for commands
* Fix bug
* Fix compile error
* Fix compile error
* Update MentorList.java
* Fix checkstyle
* Fix checkstyle
* Update AddMentorCommand.java
* Fix checkstyle
* Fix checkstyle
* Fix checkstyle
* Fix bug
* Fix checkstyle
