WIP -- Fix esc and double commits

[gabrielmontagne]

Description

Fix cell editor flakyness

Motivation and Context

The current cell value editor is a bit flaky -- might dispatch commit right after cancel or might dispatch a couple of commit events when only one was expected.

This branch / PR attempts to make it more robust.

How Was This Tested?

A version of the edit cell block has been updated to use a pre-release version with this fix:
http://bl.ocks.org/gabrielmontagne/a6aaeeef596ad1473532318d153f0836

Also, an extra rig which exposes the problems has been added, examples/edit-cells-lock-on-edit.html

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change follows the style of this project
• My change requires a change to the documentation
• I have updated the documentation accordingly
• I have read the contribution guidelines
• I have added tests to cover my changes
• All new and existing tests passed