Revert "Removed more vars from [Startup]. I think these were already moved elsewhere, because I can't find any reference to them in the code."

This reverts commit efa722786509bd8e02e23f11da974b4282dbd185.
Move AllowedClients and BannedClients section to new [AccessControl] section in OpenSim.ini from [Startup]

This change also corrects the setting names - they were actually wrong (though the text in {} was correct).
If there are settings in [Startup] they will continue to be used and anything there will override settings in [AccessControl]