Add gotxs/easy package for OT_ME wrappers

The `gotxs` should only wrap `OTAPI_Wrap*` methods.

This makes it easier to see which level wrapper is actually called. Also there
might be situations where need a higher-level and a lower-level wrappers and
needed, this way both can coexist.
Merge pull request #4 from OttoAllmendinger/add-gotxs-easy

Add gotxs/easy package for OT_ME wrappers

irc:

> `<jweiss> ttll: merge it :)`