Optimize repetition iteration control for set

We encountered a performance problem in the interaction between Flow and
Repetition. The Flow updates the visible indexes of the repetition
during the draw cycle, and was found to be taking an exobitant amount of
time.  The visible indexes updates occur as a sequence of calls to `set`
on `visibleIndexes`, each of which propagates a call to
`handleOrganizedContentRangeChange` on the repetition, updating the
value at a single index.  As such, it is possible to bypass the check
for whether enough iterations have been created (none will be created or
destroyed), and possible to avoid splicing the iteration in and out.
This optimization just changes the bound content for the existing
iterations in place.

A previous revision of Repetition, before the integration of bindings,
certainly did contain this optimization.
Fix range controller swap
First shot at a label component.
Another label option: trigger an 'activate' event on the target.
Revert "Another label option: trigger an 'activate' event on the target."

This reverts commit 209a4a919a2f341568336dc5874b930f2335f2cd.
Label action is configurable, but defaults to 'activate'
Add blueprint and test for label.
Escape key closes overlay after confirming with delegate. Code and unit tests, but the key composer just never actually sends us events
Overlay correctly claims and surrenders activeTarget.
Clean up and document formerly-duplicated code for dismissing overlay.
Overlay code review fixes:

- Document and clean up workaround for KeyComposer event firing on component rather than composer.
- Add test for activeTarget handling.
Overlays should not leak events to previous activeTarget.
Yes it should.
Remove __flowTranslateComposer from globals.
Fix Slider initial thumb position
Fix Slider not moving less than 1% increments
MON-109: KeyComposer registers events without needing to add an event listener to it.

- Include the KeyComposer tests in the main test suite. Make them pass. (All were previously failing.)
- Deprecate KeyComposer#addEventListener and ensure events are triggered without calling it.
- Special-case EventManager to look up the event identifier correctly for KeyComposer events, because the identifier should come from the composer, not the target component.
Deprecate and empty out addEventListener
Merge pull request #1313 from romancortes/fix-slider-not-moving-less-than-1-percent

Fix slider not moving less than 1 percent
Add axis property to AbstractSlider blueprint