fixes #8465 Add Digital Ocean Support (this time with fixes)

Sorry, this is a re-request from #1974 .. I messed up and had to re-create the branch.

Please see that for history.. this is intended to become a module *probably* :)
Why these comments? Thank god DigitalOcean is one of the few providers that you can reliably expect ``` Fog::Compute::DigitalOcean::Error ```, I don't think the comments add much value here