Remove cruft and add comments to explain how setLocale is called.

use VM that includes `getLocale()`

In `blocks.jsx` only call setLocale if visible. Depends on `getLocale` being added to VM to know when global locale changed while not visible making the VM out of sync.

Update scratch-paint to the latest version 

EV3/Microbit critical fixes for code freeze

Localize custom procedure modal title - per discussion, the changes to error-step are intended to avoid `i18n:src` errors

* Added localization for ‘Make a Block’
* ‘block name’ default text is in scratch-blocks

The changes in `error-step.jsx` were needed because the same id was defined in there and `unavailable_step.jsx`. The scripts to generate the json file for Transifex give an error if the same id is defined in two places. In error step it simply uses the id without redefining default value etc. The alternative would be to add a new messages.jsx file that has the definitions for shared text and include that in both places that use them.

Widen add-extension button to match category.

chore(package): update scratch-paint to version 0.2.0-prerelease.2018…

Do not skip safari 9 browser test because it works now

Updates to sprite, costume, and backdrop libraries

Goes along with https://github.com/LLK/scratch-blocks/pull/1646

Update vm again, bringing in variable updates

Share Local Variables from a target to another

Provide a from target id when sharing blocks to another target so that variable conflicts can be resolved.

Closes #2616

Update scratch vm to include promise reporter fixes

Update scratch-blocks to the latest version 

Fix rename variable bug

Update scratch-paint to the latest version 

Update scratch-l10n to the latest version 

Update scratch-blocks to the latest version 

Add a new "unavailable" step to the connection flow