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.
how does the backend default to fleet if we're passing in a requested backend? Will it default if the supplied string is empty?