In-Band Registration improvements

Hey Artur,

for my application needs, I have to proceed to a more complete registration than just username / password, so I implemented the support for custom registration form (XEP-0077 - 4. Extensibility).

The form provider is pluggable through Tigase configuration. I'd be glad to submit you the changes.

Secondly, in our application, we use a custom UserAuthRepository, and we need more informations to create users (some infos provided by the custom form), so I'd like to propose a new method for the UserAuthRepository.

void tigase.db.UserAuthRepository.addUser(BareJID user, String password, Map reg_params) throws UserExistsException, TigaseDBException

Whose default implementation should simply ignore "reg_params" and fall back to addUser(user, password) :
void addUser(BareJID user, String password, Map reg_params) throws UserExistsException, TigaseDBException {
addUser(user, password);
}

So the addition of this method is fully backward compatible and would allow more extensibility through the reg_params map. This map should be considered as "in-out", the UserAuthRepository may consume or add params during the registration process.

If these changes are fine from your standpoint I could send you a patch over the weekend.

Regards,

- nicolas