JERSEY-1535: Jersey unconditionally wraps Javascript into a JSON-P callback

 - wrapping javascript only if @JSONP is present
 - unignored tests
 - testing returned media type of wrapped javascript entities

Change-Id: If8dd01562af1726362fd11ac678245c9a42d8683
Merge "JERSEY-1535: Jersey unconditionally wraps Javascript into a JSON-P callback"