(experimental) Edit and create/replace villagers

This is an experimental release. If you would like a stable one, please use 0.51-a.

Took a while, but I've finally gotten (somewhat) real-time villager editing working.

There's a small guide here here:
https://youtu.be/5CUUZhGtsxk

Big big thanks to strawpedo for keeping an up to date list of villager files which this program uses.

Have fun!