Add 'native-ide' command

One of the few things that mfp-cli-ext did (or I hoped to make it do!) which I found very useful was to provide a command for Native projects (or indeed Hybrid ones) to open the native IDE (e.g. XCode) for the project, like Eclipse does/did. It's a convenient shortcut for a Hybrid developer at least.

Would like to port this functionality to mfpx when I get some time.
