Draft: Playback-scrubbing fixes for paused media.

This MR fixes #1719 . The progress bar (and the time /remaining time) are now updated if the user swipes or seeks while the media is paused. I do this by "faking" the UI change if the media is paused. Additionally I have added a check for media playback before the mediaPlayer.time observer calls playbackPositionUpdated() (which updates the progress bar to the playback position, which is unchanged).

Current problems I am working on:

1. If paused, Seeking multiple times does nothing. Only one seek forward or backwards is counted. Unsure how to fix this (or if I should open a new issue for this)