url service improvements:

- support POST method at user's preference
- support basic HTTP auth (uses "user" and "secret" for
  username/password)
Added Boxcar 2 support
Merge pull request #86 from mrrcollins/rc-boxcar2

Added Boxcar 2 support
Document the usage of URL basic authentication options
URL service: enable HTTP basic auth if either username or secret is set

Update documentation accordingly.
Merge pull request #85 from FruitieX/fruitiex/url_improvements

URL service improvements: