playback controls: parseFloat for font-size!
allow no-arg makeInvalidatingChange to flush props
Make duration properties always instantly update

[#79814322]

Metadata changes (removing propertyChangeInvaldates: false), in addition to invalidating props when canExportData is fired, ensure that actualUseDuration/actualDuration properties are updated immediately when CODAP communicates with the interactive, rather than only after the model is started.
serialize: serialize null correctly

Bitten by typeof(null) === ‘object’!
Alternate def of duration properties

[#79814322]

This definition will make it easier to implement a UI control for duration properties.
Define formatTime method on all playable models

[#79814322]
playback controller: replace $.proxy with bind()
add duration control to playback controller

[#79814322]