Per UX review of help text, this commit makes several changes over the breadth
of the Faces help:

* Preface API-only action summaries/descriptions with "API only." (issue #7775)
* Provide both CLI and API info in "returns," with the CLI info first. (issue #7778)
* Summaries should be sentences. (Add punctuation.)
* First sentences of descriptions should reiterate summaries. (Summaries and
  descriptions should be displayed far enough apart that this isn't a problem.)
* Standardize on "subcommand" instead of "face" when talking about the entity
  you invoke at the command line. (Use "face" when describing API use.)
* Fix outdated or clunky text in several faces.

Faces help output relies on input from the documentation methods in each
of the faces to be documented. This commit calls those methods in each of our
faces, with varying levels of detail depending on their complexity.

Add the ability to download a file into the local filebucket using a puppet
URI or from disk.  Also, the ability to store into the filebucket.

These provide at least basic UI for moving data around using the filebucket
service, and act as an example of how further work can be done.

Also, update the code to eliminate a couple of redundant checks on arguments,
and add some basic testing around the actions.  Mostly only that they exist,
at this point.

Reviewed-By: Daniel Pittman <daniel@puppetlabs.com>