More upnp support

This adds a [cling](http://4thline.org/projects/cling/) upnp service to UPNPHelper for more/better dlna feedback and interactivity (though our core dlna support is still native). Needs much work, but so far I've added
* renderer pop-up panels on the gui
* upnp remote controls if the renderer supports it
* greying of icons when offline (seems to lag a bit :-))
* methods to initiate playback from the server

Although renderer recognition should work as-is, there's a new faster  ```UpnpDetailsSearch``` renderer conf setting which is made up of any snippets of text copied (in the same order) from the upnp details on the renderer panel, separated by " , ", e.g.
```
UpnpDetailsSearch = <manufacturer> , <modelName>
```
Would appreciate real-world feedback at this point, since my Sony Bluray doesn't even support upnp control/interaction and I'm just testing with XBMC.  Feel free also to grab some aspect of this and develop it further, since it can go in a lot of directions (plus I'm getting a bit tired :-)).