style(*): add doc strings to deisctl and logger

This change quiets most `golint` warnings for the *deisctl/* and *logger/* components by adding go doc strings. It also removes several functions in the `deisctl/utils` package that were unused.

I would appreciate feedback on the accuracy and usefulness of the doc strings in particular.
I'd write

> Config gets or sets a configuration value from the cluster.

> A configuration value is stored and retrieved from a key/value store (in this case, etcd) at `/deis/<component>/<config>`. These configuration values are typically used for component-level configuration such as enabling TLS for the routers.