Give the patch-review a much needed workover

* Fix broken patch-review when committing/reviewing a subdirectory with git
* Don't forget the checked and unchecked files when updating the patch
* Make the order of automatically opened documents consistent with the file-list
* Make the 'next hunk' and 'previous hunk' file-local again, their changed behavior was very annoying
* Correctly jump to the first changed hunk on automatically opened documents
* Add 'next file' and 'previous file' actions, which respect the selection
* Don't change the cursor position for documents which are already open
* Make the file-list selectable again, this highlights the currently active document, it's very useful!
* Make the context-menu in the file-list work
* Add 'select all' and 'deselect all' actions to the file-list context menu