[KDirOperator] Add follow new directories options

Summary:
Currently, KDirOperator always calls setUrl on newly created directories.

This revision adds new option to configure this behaviour:
followNewDirectories and followSelectedDirectories

When using KDirOperator in tree mode as an embedded project view widget, we don't want to change the listed directory when creating new directories.

Reviewers: Frameworks, dfaure, cfeck, pino, ngraham

Reviewed By: dfaure, ngraham

Subscribers: dhaumann, ngraham, kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D23336