honor 'label' on fields
merge
fixed issues raised by automatic escaping.
use Traversable check, and remove debug code
make checkbox field a special case, use options for value and label
Remove the version
in Input and Select helpers, use strict equality when checking values
emulate 'placeholder' for select options
convert Input helper to use a Locator and classes. this allows adding of new Input types.
update tests
move a bunch of stuff around
- Move form helpers to their own dir

- Make 'field' helper a locator

- Make 'input' helper a locator (remove InputLocator)

- Add getField() method on form helpers to support Aura.Input array spec

- Select helper options() now recursively descends into array values as optgroups
change Input type Button to Generic and have the others extend that. No more $label and $label_attribs; instead, pass a 'label' pseudo-attribute.
Merge branch 'fields' into develop
change where PHP_EOL gets added
add field type 'repeat' for repeated field inputs
add 'repeat' field type, and refactory registries for instance script
fix configs for 'repeat' et al
add the repeat registry file
remove array typehints; messes auto-escaped objects