add path and address completions to shell and lua

[fischerling]

This just showcase the behaviour if we add address and path completions to lua and shell as mentioned in #334.

[skx]

I'll merge this in immediately, thank-you, but I will hold off further changes until I've had a few days to think about #334.

I might be being too stubborn, and too used to what was present in the past, although I do definitely like the idea of more specific completions for some cases.