Refactor Flow frustrum culling

Since repetition does not have an index map any more, this commit
introduces an alternate mechanism for managing the "indexMap".

The new RangeController supports a "visibleIndexes" filter.  This array
is functionally equivalent to "indexMap" but is implemented with FRB
(bindings).

The Flow now has an internal RangeController called frustrumController.
It takes as input the Flow's content, or the Flow controller's
organizedContent, and produces as output the content plucked with
"visibleIndexes".  The output is fed into the Flow's repetition.

The updateIndexMap algorithm is retained, but renamed
updateVisibleIndexes, and refactored to maniuplate the visibleIndexes
instead of the indexMap.
Fix selected iterations not being listen to
Fix selected iterations
Remove problematic content property from list blueprint
Fix duplicate content property
Fix scroll into view for multiple paths
Remove console.logs
Merge branch 'flow' into edge
Fix JavaScript syntax error
Remove willPrepareForDraw usage
Fix wrong classList usage
Call ToggleButton parent's enterDocument
Remove duplicate toggle-button spec
Rename _range to _elasticScrollingRange
Use draw timestamp instead of Date.now in Flow
Fix continuous drawing in Flow
Refactor InputRadio

- Extend the AbstractRadioButton from montage
- Rename to RadioButton
Remove draggability from slider thumb

The thumb is not intended to be drag-and-dropped anywhere in the
data transfer sense. This caused problem in situation where using a
slider ended up triggering the various drag events that expected an
actual drag-and-drop operation.
Fix list blueprint
Fix dimensions on play/pause icons