Refs #517, search for campaign keywords in referrer URL when not supplied by query param and use referrer hostname when no keywords in referrer URL and nothing supplied in query param.

Note: also includes quick tweak to integration test base for more descriptive error when expected file cannot be found.


git-svn-id: http://dev.piwik.org/svn/trunk@7811 59fd770c-687e-43c8-a1e3-f5a4ff64c105