bindField function for mobx-react-form
export const bindField = (form, field, {error = 'error', value = 'value', floatLabel = false, onChangeFn, onChange = 'onChange', placeholder = 'placeholder'}={}) => ({
name: form.$(field).name,
[value]: form.$(field).value,
[placeholder]: form.$(field).label,
...floatLabel === true && {floatingLabelText: form.$(field).label},
[onChange]: onChangeFn || form.$(field).sync,
[error]: form.$(field).error
});