forms: Fix saving of form config and list item props
forms: Fix display of some validation errors
forms: Restore saving of ID value for selection fields
forms: Standardize saving of choice field values

Always save a key/value hash of the selected value(s). However, if the field
does not have the multivalue configuration setting, then retrieve just the
key with the to_php() function. to_database(), however, will always return a
JSON string with the value(s) formatted as a hash array.
forms: Fixup the SelectionField wrt. multiple values

Always support and consider multiple values — even using the typeahead
widget.
forms: Disconnect toString() and getChoice() functionality
forms: Fix loading indication on dialog
forms: Selection of a choice field is not always required
forms: Fix typeahead field again (for realz this time)
Merge pull request #1183 from greezybacon/issue/choice-fields

Choice fields :: fix several minor issues

Reviewed-By: Peter Rotich <peter@osticket.com>