Implemented Join Pool/Participation permissions by User Group (per pool)

You can now specify which User Group(s) have permission to join and participate in a specific pool. This is a per pool setting and controls two factors (Join and Participate).

Join: A user can join a pool if they are in a User Group for that specific pool. This is a one time initial check.

Participate: A user can actively participate (make picks) as long as they remain a member of at least 1 User Group associated with the pool. If at any time, a member is not in any user group(s) associated with a specific pool, they will not be able to participate (make picks) until they have been reinstated in at least 1 User Group associated with the Pool. They still remain IN the Pool, they just can not participate. This is good for pools in which you have a membership group that requires a weekly fee to make picks and they can't make their picks if they don't pay their dues.

This is an enhancement to the current join system and does not take away or hinder anything already in place. This just gives administrators a bunch of new ways to use pickem.