Add conditional form field support

[postmastersteve]

Forms could allow fields to show/hide based on a selection from a dropdown/radio button. For example, a form could begin with a question about "Which photography are you interested in?" with options for family, wedding, or newborn and the user selection can show/hide conditional fields relevant to each option.

Perhaps we could limit this to a single conditional per form to simplify?

[postmastersteve]

+1 David Hammond ticket 173357

[lalunecreative]

+1