Unwriteable config files cause error spamming

[digarok]

The documentation recommends the read-only strategy (see: Modulae) for config files.

This causes the emulator to continually whine about not being able to write config file after it tries to eject the disk.

At the least, let it fail gracefully.

[digarok]

Add an option to "freeze" config, and when set it doesn't ever try to write?