VideoOverview: Improve loading progress indication of the page.

The thumbail now shows the progress indicator when it's loading.

Page contents are hidden until reply from youtube data api is received.

Signed-off-by: Peter Tworek <tworaz666@gmail.com>
YoutubeListItem: Fix comparison between image loading status values.

Signed-off-by: Peter Tworek <tworaz666@gmail.com>
Improve network error handling.

It's still far from perfect but at least the basics are handled better.

Signed-off-by: Peter Tworek <tworaz666@gmail.com>
Update TODO file.

Signed-off-by: Peter Tworek <tworaz666@gmail.com>