drop forceful ordering of EditProfileForm fields

The code assumes 'first_name' and 'last_name' will always be the last two fields
in the form. This assumption is incorrect if additional fields are added to the
form ::

    class CustomProfileForm(EditProfileForm):
	extra_info = forms.CharField(label='Extra Info')
	more_extra_info = forms.CharField(label='Extra Info')

or if the fields are explicitly ordered ::

    class EditProfileFormExtra(EditProfileForm):
	class Meta(EditProfileForm.Meta):
	    fields = ('first_name', 'last_name', 'mugshot', 'privacy')

Both produce additional first_name/last_name pairs in the rendered form, and in
the latter case they overwrite mugshot and privacy.

It seems best to leave the ordering up to Meta.fields.
https://docs.djangoproject.com/en/dev/topics/forms/modelforms/#changing-the-order-of-fields