Mutiple fixes in 7.x branch: Views handler, flag_friend_determine_friend_status(), delete friend

This patch gets the module into working order in Drupal 7.

I've found and fixed a number of issues, and fixing them is critical to my current project so for speed, I've rolled it all into one patch.

It fixes as follows:
- Views handler: Instead of adding expressions and multiple where's, It simply looks up all the UIDs first and then passes those to the query. This is probably better, performance wise, since there aren't two long WHERE IN() lookups and it makes sure to only include each UID once. Fixes http://drupal.org/node/1012296
- flag_friend_determine_friend_status() - This query was also broken, making the Flag Friend links and other things not work. I simplified it into one line.
- $form_state on flag_friend_form_submit(). Fixes the error: "You do not have permission to flag or unflag this piece of content" when trying to unfriend. Changes the action value to "unflag" instead of "unfriend", so flag.module can understand it.
- Fixes "delete friend" query, replaces with simple one line query. In the current release, you can remove a friend but they don't disappear from the friends list. Checked the return of that delete query and it was always 0, meaning, no rows deleted.