made several small changes

-admins cannot deactivate themselves...this could have caused some
problems that the front end and system should not have to deal with
-changed the exception handler to return a string instead of a hashmap
since we were only returning one string and it helped with some
formatted exceptions
-clients should not be able to double book appointments anymore
-made changes to keep inactive users from logging in or accessing the
backend
-fixed a unit test to comply with the above changes
-there may or may not be an easter egg in the backend
Merge branch 'master' of https://github.com/joubin/CSC191