Implement GET on commands returning JSON data

This implements the bones of the protocol to allow our client code to fetch
data about commands dynamically from the server.

https://tickets.puppetlabs.com/browse/RAZOR-183

Signed-off-by: Daniel Pittman <daniel@rimspace.net>
Add generated help text to the command data

Now that we have a basic protocol for fetching data about commands, we can use
that to expose the documentation added to them to the world.  This commit adds
the basic infrastructure for rendering help text as markdown, and wires it up
to the public API.

https://tickets.puppetlabs.com/browse/RAZOR-183

Signed-off-by: Daniel Pittman <daniel@rimspace.net>
Implement a basic full help template

This adds a basic template to cover the help output, and extends our help DSL
to cover a few more details that this showed we needed.  This is hardly
optimal, but is a reasonable starting point for rendering the help text
for our commands.

Signed-off-by: Daniel Pittman <daniel@rimspace.net>