Experiment: simple_form

While trying to debug some minor bugs in the form code, I wondered if we should consider using simple_form for the generic forms on the site and save angular.js for the more complicated interactions (like paginated lists and filtering).

This is an experiment in making the 'service request' form based on simple_form, rather than being managed by angular.js. I haven't taken out any angular.js code in this PR.

With simple_form, we get something that plugs more smoothly into Rails and requires less code. Without angular.js, we lose some client-side validations and need to roll some of our own code to show/hide elements dynamically.

I'm leaning toward thinking this is overall a :+1: thing, but I'm happy to hear dissent or other opinions before merging.