LPS-37724 Open Export/Import in a pop-up

Hey Julio,

I've implemented this following your advice and Nate's. I'm sending it to you only because the automatic reload after an import doesn't work due to the fact that the import is asynchronous (I think it's actually being reloaded, but too early). I've left it in a commit of its own (the last) so that you can fix it if you find a solution (or drop it otherwise).