This is because when switching from project to editor view, this component gets unmounted and then remounted, but the componentDidMount seems to happen before the componentWillUnmount. Because it is dealing with a global variable, it is unsafe to always unset the beforeunload when unmounting.

Resolves #3950.

Unfortunately the design of scratch-storage doesn't make having multiple distinct POST urls easy at the moment. So for the time being, just make this request ourselves.

use blue creating screen for new projects; revised alert text for copy, remix; saving messages don't dismiss alerts

simplified autosave code per rschamp's comments; made isShowingSaveable and autosaveIntervalSecs props

I do not like how the alert component is hyper specialized for two distinct use cases. It would be much better to refactor the alerts so that the alerter can just fill the alert with whatever they want. But I do not feel comfortable making that refactor because I know ben and evelyn have gone back and forth about these alerts.

Listen to the new project changed event from the VM and keep track of the state in Redux.  Update it as appropriate.

Known issue is that the project is marked as "changed" immediately after it's loaded. This is due to asynchronous event emitting while the project data is loaded, and needs an update to the VM to fix.

Instead of saving .sb3 files to the projects server, save just the project JSON. Save assets to the assets server. This happens via the asset types being routed to different web sources by storage.

made alert messages translation-ready
updated project saver hoc
default alerts to COLOR_ORANGE

got tests working

made neutral button color

made remixing, saving as copy states; made project state naming more consistent

changed meaning of canCreateNew to true creation

fixed project-saver-hoc test

removed Remix option from standalone player menu; renamed canSaveAsCopy to canCreateCopy

added parenthesis missing from rebase

fixed create new test