Fixed PageField to work with Django 1.7

When migrations call ForeignKey.deconstruct, it manipulates the `to` argument in kwargs.
Changed this to use `to` in kwargs instead of hard coding so migrations work.
`limit_choices_to` is not a valid kwarg for forms.MultiValueField
Merge pull request #3505 from jsma/3.0.x-pagefieldfix

3.0.x pagefieldfix