Restriced amount of displayed polygons.

'zoom_changed' now listens to nothing and 'bounds_changed' listens to
update_items; This fetches 50 biggest items inside the map viewport, removes
Google Maps shapes of unlisted items and calls update_geometry at the end. It
seems that the 'unsorted'-option causes _list/bbox-filter to crash but only if
a "vast" amount of keys is also specified. Therefore I've left it unset.
Fixed broken replication form and updated couch ip.
Fixed crash of _list/bbox-filter if 'unsorted' is specified.

This is a weak temporary fix and I have no explanation of why I have to
'exhaust' rows before the list function is finished. It also ruins my
performance in a ghastly way.