Experiment removing SET_SEEK_TO

__tests__/integration/mirador/index.html

src/components/AnnotationsOverlayVideo.js

src/components/VideoViewer.js

src/components/ViewerNavigationVideo.js

src/containers/AnnotationsOverlayVideo.js

src/containers/ViewerNavigationVideo.js

src/state/actions/action-types.js

src/state/actions/window.js

src/state/reducers/windows.js

src/state/selectors/window.js