Fix invalid links to 'index' in form partials for model names that are mass nouns.

the link back to the index page in the generated form partials should work differently for models with mass noun names (e.g. money, equipment).

The mass noun 'money', for example, Rails provides the following named route `money_index_path` instead of the one generated by the gem's generator, `money_path` (which routes to 'show')