QmlDesigner: fix regression from last filter import fix

 - adding line ending to the import code
 - set correct fileUrl to resolve local directory imports

Task-number: QTCREATORBUG-12625
Change-Id: I2861fc5674ff0fa4f6cc9e308a22cd2853ffa85c
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>