Domain Model stuff for M4
Updated Backlog
Added code to show login error
Comments and moved login button method

Added comments describing methods
Moved the login screen's login button click method from the Fragments
class to the Welcome Container with the other button click methods.
Removed unused imports

No more yellow warning signs on the files
ForgottenPasswordUseCase
Updated Backlog
Added activity_register layout
Updated Backlog
Finished activity_register layout

:DDDDD
Merge from Master

Sync contents of master with this branch.