Revert "Player: first attempt to use a custom clip path"

This reverts commit 9d9c7741e991cabddb4db64005e186baffec3f0d.
Revert "Inkscape extension: manage custom clip path"

This reverts commit e0923d59be52002fa957e0b8a66cfec8abad7202.
Revert "Inkscape extension: add a field to set a custom clip path. Better tooltips."

This reverts commit c22eec1f5688d40eb342ad9ed21b3cbac8fa9b9c.