Updated Note object. Added Edit All function. Added UniqueTagList to store existing tags and associated persons

[LowGinWee]

Note object now does not show up in UI if user does not specify it.
Edit All function to edit all listed persons by using the argument "all/"

TODO:
To update edit command description and user disclaimer
To update persons displayed to only those who are edited
To merge and to edit/update trie as per add, delete or edit via checking the UniqueTagList
To update description of methods in UniqueTagLIst.java

To update UGDG

[LowGinWee]

To xavier:
The addition of the UniqueTagList is in the following files:
Addressbook.java - the instance of UniqueTagList is created here
UniqueTagList.java

[lekoook]

@LowGinWee >
I think the UniqueTagList should map the key (Tag) to a List/ArrayList< Persons >. This will cut down the memory overhead of using UniquPersonList as well as reduce coupling between the two.
Also, I think there should be methods to add/remove/edit single Tags instead of adding ALL tags from a single person. I think this gives better flexibility to use your class.