VideOverview: Add an option to browse channel the video belongs to

This feature was requested by some users. Seeing how implementing it is
fairly easy to implement this feature, add it.
Search: Make sure BusyIndicator and "No results" label are centered

The elements were centered in page. This looks strange when on screen
keyboard is visible. Better to center them in the ListView without
taking page header into account. The elements look better this way.
Redesign ChannelBrowser page and cover.

New versions should better fit into current UI design. The
ChannelBrowser page also looks good in both landscape and portrait
modes.