Lua-based chdkptp support

This is a initial PR to bring in easier `chdkptp` support.
It uses a modified version of `chdkptp`, thus the user must build a custom version of `chdkptp` first.

The patch is available here: https://gist.github.com/adongy/55b232cfb759df4920bd

It uses `lupa` (https://github.com/scoder/lupa) to provide lua-python bindings.

`lupa` *must* be build *without* LuaJIT support (`setup.py --no-luajit`) else it doesn't work.

Remaining issues are:
How to make users install `lupa`, build the modified `chdkptp`.
Use properly the driver. At the moment, it just mimics the previous version of the `chdkcamera.py`. It should instead only use `lua` when necessary.