Extend the "verify" functionality

I think it would be helpful if any content stored in your Library you did not create was easier to stay functional with newer, major releases.

Currently people have to download the content again to use it with a newer release; instead, what if whenever we clicked “Verify” on incompatible content, it simply updated it? Additionally, the UE4 Launcher could keep tabs on updates to Marketplace content we have installed, informing us if or when a new build for that content was available.