DVB: Fix time calculations.

StartTime could have been inaccurate in certain cases.
DVB: Add channel name to snapshot filename.
DVB: Add only supported services.
DVB: Add context menu to the navigation dialog.

Use std::vector to store channel in order to get better sort abilities.
Fix: MoveVideoWindow() might not be called when needed after 7c6a1ce8af578b90c1c01067f2bfb55fce1b4943
("Don't MoveVideoWindow() during fullscreen toggle")

We need to call MoveVideoWindow() to properly handle EC_VIDEO_SIZE_CHANGED
event.

This commit fixes #4178