Re-implement rp9 support

[giantclambake]

With the new directory structure, we have the ~/Amiberry/rp9/ directory. If one copies a .rp9 files into this directory, it shows up in the Configurations panel ...however, the file does not load, and the emulation starts with the basic A500 config.

I understand this support was removed some time ago, so it really should be reinstated at some time, to properly support the functionality already evident.

TIA