Add a 'default browser' proxy object

There's also some tidying up here:

* Remove some warnings, I think it's about time we butchered/removed most of the ND classes
* Made all proxy providers conform to the protocol
* Defined a new method for `NSLocalizedStringFromTableInBundle(<#key#>, <#tbl#>, <#bundle#>, <#comment#>)` - it was taking too long to type

Things I'm still not happy with:
All the proxies are defined in the core app. They should be in the core plugin really. I can't be bothered moving all the classes right now though