Add test for setup_create error message
Use the messages framework for setup_create view
Add test for setup_invite error message
Use the messages framework for setup_invite view
Add test for manage_player error message
Use the messages framework for manage_player view
Get rid of the 'do_result' function and use the messages framework instead
Remove the 'do_result' function from 'grandchallenge' module and add a template for displaying messages