Invite user plugin needs to report password requirements so that people can enter in their password.

1. Set a password policy in JIRA.
2. Invite a user to JIRA.
3. Click that user's sign-up link.
4. (BUG) Enter in an invalid password. The user will get no idea what is invalid about the password. We need to list the password requirements.

It might even make sense to list the password requirements on this invite page so that the user does not have enter a password to find out what is valid.