Fixes/tests for create_user and change_passwd scripts

[jschnei]

Fixes (and adds tests for) the create_user.py and change_passwd.py scripts. Most of the existing script logic has been merged into dao.py.

Also changes the password of the admin user in the test db to 'admin' (i.e., you should now be able to log in as 'admin'/'admin' on the webapp in the test env).

[jschnei]

• Removed all the old fb users from users collection (the only admin user left should be admin/admin)
• Added list_users.py script to list the current users in the users collection (should address write test code for admins being present in "test" db #28)

[jessemtso]

all tests pass, squash and merging!