Deprecate permgen attributes in the management model

The permgen size attributes no longer do anything in a core 2.0 or later server, as we require JDK 8 and our code ignores these if JDK 8 or later is running. So we should deprecate the config elements and log a message if they are used.

Part of the parent task for the management model itself. I'll do this in 2.0.5 because I don't mind tweaking the API in a micro just to add deprecation information.