Merge branch 'develop' into feature/switch-languages

package.json

src/components/backpack/backpack.css

src/components/backpack/backpack.jsx

src/containers/backpack.jsx

src/containers/costume-tab.jsx

src/containers/sound-tab.jsx

src/containers/sprite-selector-item.jsx

src/lib/drag-constants.js

src/lib/make-toolbox-xml.js

src/lib/sortable-hoc.jsx