GUI for selecting jconf files

[rpavlik]

NavTestbed should offer a GUI that allows you to create (one or more?) sets of jconf files to use, and select a set to use as default. The data persistence mechanism is already set up - /etc/vrjlua-config.lua is designated for this purpose. While it can be hand configured, that's a drag, and doesn't give the opportunity for switching between multiple easily. (Mono, stereo, simulator, for instance)

This setting should be persisted in /etc/vrjlua-config.lua (relative to the root of where you have vrjugglua, of course) rather than a user-profile-wide setting so that it is both portable and allows testing with multiple setups to proceed without interfering.

cc: @jscasallas @lpberg