Select boxes for multiple stacks

I've added select boxes for multiple stacks, this will only show if  ```defaultStacks``` is added to ```deploy.json```

I've tested this manually with Status App and it works. Hooray. Looking up the tests it looks like I could add something to ```Testing.scala``` but it might be worth doing this when I've updated the deployment view page to output the stack being deployed too (I'll do that as a separate PR).

I've changed ```checkbox-selection.coffee``` to work with classes not ids however I couldn't find an example to check both hosts and stacks work as expected. The first example I think will be the API indexer but there is still work to do on that side.