Add simple "go-wrapper" script for building and running, especially to accommodate ".godir" support

Fixes #4
Fixes #9

Also, `update.sh` will make sure it's properly copied into each version subfolder, like we've done with other official images.
oups, `install` is really `get`.

Sorry for the missunderstanding.

What about going for `go-wrapper get` and just passing the arg verbatim.

That way people using the wrapper wouldn't have to rely on the usage.