wms proxy

DO NOT MERGE or MERGE AT YOUR OWN RISK!

Down the rabbit hole, a suggested fix for #946. I saw that authenticated geoserver requests go via the proxy controller, so why not just run them all through?

Have a crack at:
http://dfruehauf.emii.org.au

Still more work to be done here. I think that in general there should be a designated `openlayers` proxy in addition to the ProxyController.
So, have a look at:
aodn-portal/web-app/js/portal/prototypes/OpenLayers.js:166 the `proxy()` function. Perhaps we can decipher together what's the idea behind it. But it seems like this is OK.

I'll add another test to emphasize the idea of that function.