Change operation and description field for user2userpoints

Usernames were added with the patch here: "Let recepients see donar username" http://drupal.org/node/917204
However, this patch adds "From: user" "To: user" in the operation field and leaves the description field blank.

I did not like this so I made a patch.
It adds the following values in the "operation" fields: "give" or "receive".
And now puts the "From: user" or "To: user" in the description field.
This patch is rolled against the latest dev.

Usecases where this could be useful:
- make a list of given / to
- make a total count of points received from other members.
- ...

Suggestions for are welcome.