added sha256 function to lua controller

[Darin755]

This is a simple solution for #689

[sfan5]

What about sha1?
any documentation that needs updating?

[Darin755]

sha1 is not secure as it has known hash collisions. (where two different inputs get the same hash) It also is pretty easy to brute force.

I could probably add this to the docs. However, the lua controller docs are dated and not great so if get around to working on docs I will likely make some big changes.

[sfan5]

It looks like the documentation isn't even in this repo, so should be fine as is.