shells: reorder methods for consistency
videoLinkShell: don't store mediaView progress

this is only necessary in remixView
tests: use valid shell model data in tests

also, create fresh view options for every test
shells: rename progressPercent -> percentProgress
shell: add remixView.percentProgress method

simplify videoLinkShell and splicedVideoShell remixViews with
percentProgress method
shell: add remixView.progressFromPercent method

simplify videoLinkShell and splicedVideoShell remixViews with
progressFromPercent method
progressBar: contentView now owns progressBar

progressBarView and shellMediaView now interact through events that
bubble up and down
contentView: remove progressBar handle