Saving searches

[NomadicDaggy]

If/when we re-enable user login at some point, it could be a nice feature to let logged-in users save and share interesting search results.

So the user searches playlists by tracks and the found playlists are funny or just interesting or there is a share-worthy pattern in the results, so we should let them share that.

At the very least, we should change the url, so that you can share a link to a specific search (just the track(s) that was searched by). We probably won't be able to guarantee the same results in the future, because we are going to be adding playlists constantly.