Fixes #6919, do not check for host in regex group in log importer if format has no regex. Also add nginx json log to log importer system test.

Add --core option to screenshot test runner so plugins w/ git repositories aren't tested in the piwik-ui-tests build.

unset a possible set idSite in the logout url, this should fix the error message not having access for idSite after logout.

fixed some system tests. the order change of some device reports changed as they have sometimes same orderid and as we moved some ecommerce reports it results in a different order now