Get rid of the last remnants of FormAlchemy

Still in pip-requirements and:

```
ckan/config/routing.py:267:    ##to get back formalchemy uncomment these lines
ckan/config/routing.py:268:    ##map.connect('/group/new', controller='group_formalchemy', action='new')
ckan/config/routing.py:269:    ##map.connect('/group/edit/{id}', controller='group_formalchemy', action='edit')
ckan/lib/field_types.py:8:    import formalchemy
ckan/lib/field_types.py:250:            raise formalchemy.ValidationError(e)
ckan/tests/lib/test_field_types.py:1:import formalchemy
ckan/tests/lib/test_field_types.py:60:            self.assertRaises(formalchemy.ValidationError, DateType.form_validator, date_str)
```