Clean up HTML types

[jamesaoverton]

• 'select' uses an HTML <select> element, but this does not allow all invalid data. I think we should always use typeahead fields instead, for this reason.
• 'search' should be renamed to 'select'
• add 'mutilselect' option
• should fields with get_matching_values automatically be 'select' (or 'multiselect')?
• should HTML types be automatic, unless overridden with a custom type/class?