jQuery: Making generated ids easily overridable
jQuery: Making generated ids easily overridable

The ids were previously prefixed with 'new_', which we found useful,
but that was removed when #199 was fixed.

Stellenticket/nested_form,tomasdundacek/nested_form,dhunnapotha/nested_form,partheey-vakilsearch/nested_form,jweslley/nested_form,cuongnguyen2503/nested_form,tomasdundacek/nested_form,pinglamb/nested_form,Stellenticket/nested_form,cuongnguyen2503/nested_form,partheey-vakilsearch/nested_form,pinglamb/nested_form,ryanb/nested_form,ryanb/nested_form,cuongnguyen2503/nested_form,dhunnapotha/nested_form,dhunnapotha/nested_form,alphagov/nested_form,alphagov/nested_form,jweslley/nested_form,Stellenticket/nested_form,jweslley/nested_form,pinglamb/nested_form,partheey-vakilsearch/nested_form