move the media search formlet up

Currently the search box is below the media file list, where it is
effectively inaccessible in a namespace with lots of files.  This
change moves the search box above the media file list and below the
upload form.
fix the default ordering of media files to be "natural".

also allow the order to be specified in more places.
show media files in date order (most recent first) after an upload is completed
Merge pull request #263 from splitbrain/mediamanager_list_ordering

Mediamanager list ordering