Smooth time remaining, bitrate and stabilize user information

Smooth time remaining, bitrate and stabilize user information

Besides the existing moving average, a smoothing factor is introduced for the time remaining display as well as the bitrate.
Furthermore, half of the buffer needs to be filled before the first prediction is displayed to the user. This reduces volatile and jumping durations towards the user and improves usability.

Signed-off-by: Cyrill H. <phlogi@posteo.de>
Co-authored-by: Carl Schwan <carl@carlschwan.eu>