Add params, use open-uri

[sjoeboo]

This PR does a few things:

• Adds a params.pp with new parameters allowing the end user to set the cache_dir, cache_ttl, and api_url (there is a sandbox.api ). This moves the defaults to params.pp per usual and init.pp inherits from that.
• Swaps out how the fact talks to the api, officially from Dell sending the apikey in the URL is a no-no, and the api can accept the apikey in the headers, so this swaps out the http work for a method that does that.
• Otherwise just sets up the fact to use the cache_dir + ttl from the config written, as well as the api_url.

(FYI, a private PAI key can be obtained by asking dell, there is a...enrollment process)