If the CouchDBImpl is calling methods on the driver, then they need to 
go here (because it could be any implementation of this interface). So 
start(), stop() etc are inherited by this interface.

A good example is JavaWebAppDriver declaring deploy/undeploy methods.

Many places where we declare other methods, it's probably a code smell. 
I think some declare getRunDir(), but that suggests perhaps the method 
needing to know runDir should be pushed into the entity.