Enable users - first pass.
Stripping user-
Fakebackend and tests expect the new auth tag format.
Fix lint.
Attempt fix for functional tests.
Split Logout and Get started buttons. Made user dropdown logout button work.
Merge pull request #673 from huwshimi/move-logout

Move logout

This separates the get started and logout buttons and makes the logout button work in the user dropdown.
Prepend generated credentials with 'user-' in fakebackend.
Merge pull request #672 from makyo/enable-users

Enable logging in with users other than admin
Lock username if juju version is less than 1.21.
Improve version parsing.