This was already being used for sb3s and sprite3s, but the code was repeated in different places. Make a single helper that downloads blobs, and make all download paths use it.

Since the common use-case is download/edit/re-upload, and we do not want to explode the storage size of assets (which are considerably larger with fonts inlined), just do what scratch2 did and do not inline the fonts. This is not ideal if kids want to use the costumes for other purposes, but until we can create a way to strip inlined fonts before uploading to the asset server, this is the conservative way to go.

This reverts commit 97f8eb63, reversing
changes made to 2e017f06.

This is used because the sortable drop is also used for general dropping as well as sorting drop, so you need to be able to drop into a sortable list that does not contain any items.

Make the corresponding reorder code be more careful to check if there is a newIndex.

don’t let `react-tooltip` decide on placement for the action menus. Force left or right depending on language  and the location. (It turned out there were other places it overlapped, the sprite selector was just the most obvious)

Questions:
* should the message strings include the number? Or should that get added to the name when the name is defined
* added a new ‘shared-messages’ to handle the definition of backdrop, costume, etc which are used in multiple places, they’re all related to defaults, so should it all be in `lib/default-project`

* 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`