License server grace period

Current behaviour is to block all users from connecting if the host server cannot validate its license against the Connect Wise licensing servers. This appears to be a one time check and the server does not attempt to re-validate. The only way to recover the situation is to reboot or restart the Screen Connect services - customers can then take an hour or more to re-appear as online.

1. Implement a periodic license check, so if an invalid license is detected or the servers cannot be contacted at the time of the check there is an automatic retry period and then re-validate users

2. Implement a grace period of say 24 hours for an invalid license check or license server issue before disabling all users to allow for any intermittent connectivity issues to the licensing servers