Home screen modified

	Removed:
		TextBoxes - username and password
		Buttons - save and cancel
	Added:
		Spinner for usernames
Changed ManageUser activity screen

	Choosing ManageUser from action bar now shows
	3 options
		ADD
		UPDATE
		DELETE
Update button is functional

	Update button in ManageUser calls EditFragment
Changed Update button name to Save
Changes in FragmentEdit

	*Made changes in FragmentEdit to accomodate it for both
	 add and update option
	 -if add_update = 1 -> add option
	 -if add_update = 2 -> update option
	*add is yet not functional
Added onClick event for Edit button
Major changes to reach FragmentEdit

	*Add and Edit button both need to access FragmentEdit
 	 from ManageUser activity through UserDatabase
	*add_update=true/false value differentiaties between add and
	 update
	*In additon, removed Delete button from UserDatabase's
	 activity
Add button is now functional

	Made new insert function in DatabaseEngine
	Made a few extra checks than previous implementation
	Redundant records will not be added
Removed unwanted comments
Disable/Enable spinner

	Spinner enabled and disabled on switching
	between edit fragment and userdatabase activity
Fixup the MainActivity after the design change by Tanjot