Corrected implementation of login

- instead of having separate pages for guest, admin and user, have one
page but the controller will assess some conditions to check what
buttons/text should be displayed in the view. This eliminates need for
multiple pages with repeated code. Just need to add in condition checks
in view/controller.
- display home_page instead of guest_home_page in home/index
- home_page can be used for all 3 types (guest, admin, user)