housing: added update pic feature to edit listing page

This is my final commit.
GGC Talk - Housing is fully functional.
Available Features:
- add new listings with a max of 4 pics each (must be registered and logged in)
- search listings with search bar
- view listings (however, you must be logged in to view contact info)
- manage your listings:
    - view listing previews
    - edit listing info and pics
    - delete listings