Retroleap v2.0.0-alpha6

Another WIP release for testing.

Changes:
-Persist new ECDSA key format to avoid known host errors in ssh
-Build gmenunx and launch it by default for lf2000
-Add retroarch cores to gmenunx (new script to generate core files)
-Move configs (gmenu and retroarch) to live in /configs
-Pick machine-specific retroarch config and copy it to retroarch.cfg (so gmenunx will work)
-Add separate build for lf2000 RT/OC kernel (from DCFUKSURMOM) - works with latest version of sshflash

Known issues:
-Brightness control in lf2000 is backwards (turning brightness down turns it up)
-Need separate retroarch config for didj (different button mapping)
-ohboy config on didj is broken/not reading configs
-Missing filename extensions in gmenunx on a couple of cores