Create Nimbus Verified Proxy Go Bindings

[dlipicar]

You can look at:
https://github.com/logos-messaging/sds-go-bindings
https://github.com/logos-messaging/logos-messaging-go-bindings

I think both use this framework: https://github.com/logos-messaging/nim-ffi
I'm sure it can be done simpler, but didn't investigate myself. Just looks too complicated.

At this level, you only write #include <verifproxy.h>. Library should be linked externally, as well as include dirs should be set externally.

You can have nimbus-eth as a git submodule here for development purposes, but it should be linked to Go bindigns with CGO_LDFLAGS and CGO_CFLAGS.