Ensure form_fields defaults to form's object value

This was working previously, but this adds a test to ensure that the
form_fields method will use the existing value on the form builder's
object.
Load all files in /lib/options/type/

This makes it so when we add types we don't have to add an explicit
require here.
Add string option type

This will be useful for simple options like leader.
Extract leader option to use string type

This also introduces the FormHelper class to extract the view related
code.