Make delete button accessible

Add Jest-specific linting rules

Adding this caught a couple of important things:
- The sound integration tests have a `.only` in them
- The project-saver-hoc tests had two tests with the same description, causing possible confusion if that test broke

Also noticed that Delete aria label was not localized.

Update scratch-l10n to the latest version 

Update scratch-vm to the latest version 

Update scratch-vm to the latest version 

Remove test.only

Update chromedriver to the latest version 

Greenkeeper/scratch blocks 0.1.0 prerelease.1564581595

Update fade icons

Prevent default when dragging trim handles to prevent image drag

Do not update trimmers only if both have not changed

Closes #5034

Sound editor update: selection-based editing

Roll forward scratch-svg-renderer

If the delete button is the current active element (e.g. focused by tab) make hitting ‘space’ or ‘Enter’ do the actual delete.

Don’t use default focus style it’s ugly.

Don’t allow the image to be dragged.