config: bugfix: update config.css uri
shells: make timeTotal a shell-wide model property

duration defaults to timeTotal
videoLinkShell: add loops property manager
videoLinkShell: differentiate single-loop duration

duration is now the total duration of the looping video, while
singleLoopDuration is the duration of a single loop
util: support times unpadded with zeros
timeInputView: optionally do not pad time
controlViews: add play and pause controls
slideshowShell: build out basic functionality