add delete button to /repl

[Rich-Harris]

Now that we have the ability to delete apps from /apps, it should be straightforward to add the ability to delete a single app from within /repl (albeit by requesting a DELETE from /repl/[id] rather than a POST to apps/destroy). Need to figure out what happens on the page after you've deleted though

[Conduitry]

Need to figure out what happens on the page after you've deleted though

Bringing you to the /apps page seems like a straightforward and sensible thing to do after deleting the current REPL.