Add simple form

Dan - this PR add the [simple_form gem](https://github.com/plataformatec/simple_form) to the project that helps, er, simplify the forms! It makes for much easier reading of the forms and has a nice `error_messages_for` replacement that can just be dropped in for form errors.

I've replaced the forms in samples/genomes/experiments where I can - although experiments is bit 'different' in terms of the data it collects, so that has been left for the most part.