Fixes #2967

 * Adding new required parameter --url to be set to piwik URL
 * now testing the piwik URL by calling API.getDefaultMetricTranslations and checking we are querying a piwik server indeed
 * web cron, when SU token_auth is passed, should still work

git-svn-id: http://dev.piwik.org/svn/trunk@5881 59fd770c-687e-43c8-a1e3-f5a4ff64c105