Edit / Delete contact implemented

Extension greatly appreciated.

Have now implemented Edit / Delete features. Button added to main menu
for edit. List view utilised to select contact to edit, interface
constants used to determine which activity calls list view so it knows
to call view or edit. Image deleted from local storage if new one is
selected. New image written to storage. Dialog option to confirm
deletion. List view refreshed when activity comes back to front.

Happy with app now, felt incomplete without these features.