Hooks for logging and IP blocking

[kitchin]

Any interest in adding a few hooks? I made a custom version with hooks back in 0.33 days and have now updated it for 0.48. Two purposes:

1. Log persona failures & successes. This one needs browserid hooks.
2. Block by IP. This one probably needs browserid hooks to do it nicely. I'm blocking the login button itself and replacing it with a message, as well as double-checking before forwarding an assertion.

I'll post a branch if there's any interest. My code does not do the logging or blocking, it's just hooks, in 3 different functions (Handle_error, Check_assertion, Handle_login).