The finder should search directly in $directory if it's an absolute sub-path

In the finder, when an absolute sub-path is defined we should add it to the path used by the iterator. So we will check less files and directories.

To test: add an extension with a lot a files (ie: abbc3) and a listener wich use the controller helper (ie: the newspage extension). It will take a very long time (between 0.5 and 1s in this example).