Use current active user count to determine whether license is valid

Previously, the EE license check used the historical maximum to determine whether an admin has enough seats for the license. Let's say a customer has a 5-seat license, and sometime during the year he had 20 users. If he/she trims back to 4 users, the 5-seat license won't work anymore. Right now the workaround is to issue a license for 20 users.

Closes #550