A few places we used an option of 'imaginaryi', which isn't a real option.  Doesn't change any behavior.

Files are properly copied in both implementations of safe_exec, and a new python_path argument adds to the python path.

Implement safe_exec on top of jailpy (old unsafe safe_exec is still here); Remove some crazy stuff from the context; always pass globals and locals, locals are the things that can be changed.