examples: add some examples in Lua using lgi library

examples: add some examples in Lua using lgi library

[libnm]     https://developer.gnome.org/libnm/1.0/
[lgi]       https://github.com/pavouk/lgi
[lgi-guide] https://github.com/pavouk/lgi/blob/master/docs/guide.md

On most distribution just install lua-lgi.

Note:
There is a bug in lgi. It doesn't handle GPtrArray corectly. It results in
crashing on list-devices.lua and list-connections.lua.
I will send a patch to lgi to fix the issue.