Add fast-farward/rewind, progress bars, menu icon and fixes/improvements.

Add support for fast forward and rewind. (long click select button to switch volume buttons to seek buttons)
Add seek and volume progress bars. (custom progress bar code from Katharine/peapod ported to SDK 2.0 with vertical bar support)
Add menu icon.
Automatically refresh every minute.
Fixh a couple rare JS crashes.
JS: Improve handling localStorage data.
Store `controlling_volume` (what the up/down buttons are currently doing - volume or seek) in persistent storage.
Other fixes and improvements.