Add content migration to the launcher

Here’s a little idea I’ve been thinking about. Right now when you want to migrate content from one project to another you have to load an entire project just to select the directories to migrate. Why not just create a “Migrate” tab under the library option in the launcher, and then select the migrate project and the directories. This would be a bit faster and since migrating seems to be something that happens with every update of the engine, it seems that making a high speed migrate option might be a good idea.