ER: document that AppleShare needs to be installed from GS/OS disks to use MacIP

[IvanExpert]

With MacIP proven to work via macipgw, once we provide some user-friendly presentation in A2SERVER, we should document that in order to use it with A2CLOUD, AppleShare must be installed. Perhaps this belongs on the GSport AppleTalk documentation page.

It's undesirable to preinstall AppleShare unless the user wants it, because AppleTalk must be enabled on slot 1 or 2 to avoid two startup-blocking error screens. (It is preinstalled when using the netboot version, because of course then AppleTalk is already enabled.)