Show username block in sensing

Add 'story' letters to libraries

Show a coming-soon backpack

Make costume, sound and sprite tiles draggable.

Make new default backdrop included in build

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

Add sound library tags for legacy sounds

Closes #1949

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

Add tags to many sprites and sounds

Closes #1949

Fix default costume index for cat sprite

Do not clear list monitor input when reselecting

Tests adding a list through the UI, the add <thing> blocks, the reported value and adding items using the monitor UI

Force a min viewport size to scroll around the UI instead of breaking

Feature/refactor gui store

Needed for https://github.com/LLK/scratch-www/issues/1874

chore(package): update scratch-render to version 0.1.0-prerelease.201…

Closes #2122

src/containers/blocks.jsx had changed referring to redux state that needed to be updated to use `state.scratchGui`

Hide block inputs when entering fullscreen mode

Move guiMiddleware to `reducers/gui.js`, and use it in `app-state-hoc`

scratch-gui exports `index.js` instead of just GUI container.

Since compatibility-testing got switched to use the player mode, it doesn’t need any of the stage/controls components.

* Export initial states for each reducer
* combine all gui reducers (excludes scratchPaint and intl)
* combine all initial states to create default guiState for preloading in www
* expect all of the gui state to be accessible at `state.scratchGui`