QUrl: add "QUrl adjusted(options)" convenience method.

Change-Id: I5eea3e0dc7b56b88a56d813207b04661b8f05a55
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
QUrl: add RemoveFilename to UrlFormattingOptions.

This allows to find the parent directory url using
url.adjusted(QUrl::RemoveFilename).

Change-Id: I1ca433ac67e4f93080de54a9b7ab2e538509ed04
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>