Navigation drawer for tablet layouts

These rather messy layouts have been added mainly to stop the tablets
crashing completely and they are rather sub-optimal. The slide-in
library browser was designed with phones in mind having only used
Mupeace on a phone.
Swap song list orientation on landscape tablets

since when displayed in a panel on the main activity, it's actually
quite narrow

This should be made to apply only to the embedded browser, not to the
separate, full screen browser activity.