sudo make me a browser

[Jason Gerard DeRose]

I had Tara try apt-get install without sudo, then with sudo, and then showed her the XKCD "sudo make me a sandwich" comic, and now we have many running "sudo" jokes in the house.

This is a bug to track landing the foundation of the Dmedia browser. I've got some rough work in progress UI in place, plus a whole bunch of plumbing that was needed.

Soon we'll use a custom URI handler GStreamer plugin so the video playback doesn't use HTTP, but for now as a stop gap, we're playing back from the native Dmedia HTTP server, which means I had to make some changes:

 * It now properly handles HTTP range requests (lesson learned: WebKit wont play your video unless you return a proper 206 Partial Content for range requests)

 * It now also returns the proper Content-Type, plus the importer now saves doc['content_type'] (which is where the file server gets the content type from)

This isn't quite "done" as in as all the features we want in the browser, but this is a good stopping point to check this into trunk before the next steps, and before this turns into crazy big diff happy fun time.

[Jason Gerard DeRose (jderose)]

Ah, I should note that although video playback is working (as is silky smooth), there is a bug where GStreamer/WebKitGtk hangs sometimes when you switch between videos by changes video.src on the <video> element:

https://bugs.launchpad.net/ubuntu/+source/webkit/+bug/906784

https://bugs.webkit.org/show_bug.cgi?id=74986

I think this might be a fairly minor, easy to fix bug, but as it stands, it's pretty hard to actually use the Dmedia video browser.