Cfy 1272 allow any distribution when installing agents

- removed specific distribution forcing.
- added ability to specify any known agent resource in blueprint under cloudify_config
- supplied download_resource_on_host and get_resource_origin_url functions.
- download_resource_on_host will attempt to use either wget or curl.
use print platform.dist()[0] (remove parentheses).
we actually saw some issues about this at rbs, the parentheses messes up the command on redhat