Allow generating a full Shiny app (ie. an actual "app.R" file) that just hosts a form

[daattali]

The main use of the package is to provide Shiny modules (but users don't need to know that, it abstracts that complexity away from them) so that a form can be plugged into any Shiny app. But it could be nice for people who want to make the form an entire standalone app to let them do that (a couple women from runconf16 told me they'd love that)