Added a custom class for the footer and header bars, allowing for the use of progress bars in the header/footer to show the duration of the track.

I also tidied up how players should return the duration and current position of the playing track.

Made some syntax tweaks and removed variables from instance scopes if unneeded.

TODO: Need to make the columns of the footer/header collapse down in size, as well as correctly applying colouring to the progress bar.