Resolve "Create simple login page"

Closes #12 (closed) Creates a login page and basic authentication. The authentication currently uses the BCryptPasswordEncoder password encoder for extra security when storing passwords.

The admin class is renamed to user so that we can use it more generally. To distinguish admins from users there now exists Role's which can be assigned to instances of User when they are created.

Currently, the redirect of the login goes to /home this can in the future be changed to redirect to the previous url by using SavedRequestAwareAuthenticationSuccessHandler in WebSecurityConfig.