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.
fixed. weird.. it's supposed to work all the way from python2.6 to 3.

Btw, we'll need this when we plan to support 3.