Remove maintainer as we now use a common one.

This is pulled from the chaindrive protobuf.
Add Gear specification, isolation and provisioner.

This is mainly what I think is necessary to define what a Gear will
actually build. In the example I am using (Ruby) the isolation is likely
irrelevant as it should technically work with anything.

But for something like MySQL there may be configurable options or
processes (hooks, etc) that can be run. I still need to think about this
a bit further.
Add some examples for commands.