Fixed bbox filtering

To play with bbox filtering, uncomment the line at https://github.com/aodn/aodn-portal/blob/fixed_bbox_filtering/web-app/js/portal/ui/openlayers/MapOptions.js#L84

Note this (temporarily) removes the spatial filtering ability in the portal.  Hoping to get this properly finished off today - part of the reason for putting this up is so that others can help.

If it's not completed, we can revert the merge of this PR (if and when we need to) - so don't fear too much about the temporary removal of functionality.