Create an “authorization workflow” so that only authenticated users can access data.

[sanehirakenji]

Accomplishes bullet point 2 in the Phase 5 guidelines. This pull request definitely has a lot of changes and deletions to files as the following was accomplished:

• Created new login files using the FirebaseAuth packages that allow for the authentication through firebase to occur.
• Created a new "Add user" page that appears if the user is logging in or registering without a "User" object that is associated with their email address.
• If the signing in user has an account already they will not be able to access this "add user" page as it will only be there upon first login without an account.
• In accomplishing the above, deleted login.dart, signup.dart, and createprofile.dart.

Note: The Add user page does not yet have a working image section and this is something that I believe that we should look into after converting all of our classes to Freezed and implementing our Firefoo database.

I would highly recommend testing this branch (issue-128) out for yourself and seeing how this new authentication system works. Currently the firebase has all of the mock data and now you are able to create your own profile as well on the application. Please do not use your real password though as I will be able to see it.

[michho8]

Great work! I assume I wouldn't need to finish the signup issue then?