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

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.

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

Fix rename variable bug by always passing additionalVars to the scratch-blocks prompt callback. Let scratch-blocks decide whether or not to use the additional vars based on whether the variable is local or global.

Depends on https://github.com/LLK/scratch-vm/pull/1321

Eliminate warnings and errors due to library item text (name and desctiption) being localized components instead of simply a string. Some are not localized (e.g. LEGO EV3), so either string or component is possible.

This is not yet implemented in the VM, but will be needed when it is.

Allow specifying variables as local vs. global. Pass var names from VM to scratch-blocks for checking for conflicts in all sprites when attempting to create a global var.

that I accidentally removed

Convert `extensions/index` to jsx and use react-intl to define/translate names and descriptions.

Another approach would be to have the title be part of what’s imported from `lib/libraries/decks/index.jsx`