Supporting GUI changes for extensionification

Comments slightly tweaked from kchadha's suggestions

Co-Authored-By: Karishma Chadha <kchadha@media.mit.edu>

Update l10n to the latest version

Update scratch-vm

Greenkeeper didn't do this for me... not sure why.

Show libraries before loading their content

Use a "title card" instead of video if using Scratch Desktop

Because the video steps get replaced by an image step if offline, we should not show items that would result in having no content

Update scratch-render

Update scratch-vm and scratch-l10n.

Make surprise and library backdrop additions NOT select the stage

fixed project loading tests

chore(package): update scratch-vm to version 0.2.0-prerelease.2019060…

Closes #4894

Revert "Revert "Pause video on tutorial window shrink""

Update scratch-render to the latest version 

Revert "Pause video on tutorial window shrink"