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.
Perhaps it could be improved by introducing a common function, say `Portal.utils.Url.proxy()` to do the construction of URLs.

Then

```javascript
    return proxyURL + encodeURIComponent(this.server.uri);
```

could become:

```javascript
    return Portal.utils.Url.proxy(this.server.uri);
```