And implement toggle on player playground

Fixes issue with changing language, and hopefully player/editor mode (untested).

This is for demonstration purposes, if this is the way we decide, I will make official APIs on the VM and the Renderer for checking for the canvas and renderer.

Hide category scrollbar for blocks for webkit/edge browsers

Use translations from scratch-blocks to generate menus

Using the new `ScratchMsgs.translate` function to generate localized menus and default values in the toolbox.

Update scratch-blocks to the latest version 

Added automatic detection of locale from browser langauge

Sprite3 Save/Load

Got rid of extra Edge x on monitor list

Fix the sprite layout by making the layout code apply to the wrapper

Locale detection function that checks browser setting and lets URL parameter (locale= or lang=) override the browser setting.

Update scratch-blocks to the latest version 
Updates the scratch_msgs to support many locales.

Update scratch-audio and scratch-vm

Fix 2px error in stage sizing

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

Initial version of loading or switching language.

Updates to How To Lib for ISTE

Additional menu item for explicitly adding from Library

Changes to language in "File" menu

Various fixes & additions for library assets

Closes #2402

Localize category names in default toolbox