Implement the Activities methods of the API

[malkam03]

The following methods must be implemented:

Method	Resource	Param	Body	Result
GET	https://url/activities/	BranchID*, ChapterID*	-	All IEEE activities of the chapter(if none provided, all branch activities)(if no branchID provided, return all IEEE activities)
PUT	https://url/activities/	BranchID, ChapterID*(if not provided, the activity is inserted in the branch)	Activity List	Status code
UPDATE	https://url/activities/	BranchID, ChapterID*(if not provided, the activity is inserted in the branch), ActivityID	Activity(blank are left unmodified)	Status code
PUT	https://url/activities/users	BranchID, ChapterID*(if not provided, the activity is inserted in the branch), ActivityID	User	Status code
DELETE	https://url/activities/	BranchID, ChapterID*(if not provided, the activity is inserted in the branch), ActivityID	-	Status code

* optional parameters.