Try to fix missing/wrong position sliders when creating TimelapseOverview and TimelapseMiniview.
Migrate some widgets to _modifyListeners for Inspector event management.
Convert TimelapseOverview to use _modifyListeners.
Move mark mapping functions for timestamps and records to TimelapseRecording.
Make TimelapseGrid associate with just one recording. Make TimelapsePanel do the appropriate switcheroo.
Fix bug where no record is previewed if TimelapseGrid slider is dragged and dropped without actually moving. Closes #129.