If the users exceed the license limit via AD, a warning message should emerge instead of disabling repo push

Steps to produce

1. Setup Stash with limited users limit (e.g: 10 users).
2. Setup JIRA or any user directory and add over 10 users.
3. Sync the users to Stash.
4. The following warning will appear in the header for all users:

   You have more users than your license allows. Pushing is disabled - purchase a license today
   

   You can see the screenshot as well:
   

What to improve
The wanning message is not really feasible since is shown by all users and can cause some frustration if the admin is not aware of that. Instead, would be feasible to have Stash deducting the user license limit first, warn the admin about the exceeding users limit and let him/her to decide to proceed or not.