added EHFormModel class
implemented behaviour to map a form field to a key path on the model
update form field cell values from model
fix issue when key path doesn't exist for a form field
set the field value when the text field is done editing
sample model to use on the form. log when the fields are set
defocus a field if the view disappears or if the view starts scrolling
Merge branch 'feature/ticket-6' into develop