Userpoints integration is duplicated

Issue Summary

Hi,

In Drupal 6, both the referral and referral_userpoints modules provide integration with userpoints. If someone installs them both, as I did, these are the effects:

* Users will be credited points twice upon a referral
* The userpoints settings page will be broken, as both modules integrate with it

I'm not sure whether you're trying to migrate this support into the referral_userpoints module, or trying to obsolete this module, but a route should be chosen! :)

Neil