#112464 standardize validation in field rather than widget, standardize use of $items rather than $node_field

 in content.module)

- updated .pot file

unifying how single and multiple field stores empty field (store 0) - hopefully the last fix for this noderef series, sorry for the back and forth dance

#87030 add blank option when not required to nodereferece, #89717 add views filter options to nodereference

of forms. Those using views.module may have to re-save views after this change.
Custom node templates will need to be renamed.

- the field is multiple valued
- no fields are filled in

code. This will require fixes to any themes that rely on the node data
structure previously used.

Added a $node_field parameter to hook_field() and hook_widget(). This eases
a very common pattern of getting and setting this value. While $node is still
passed by reference, fields should *not* modify it. Instead, modify $node_field
which is saved back automatically.

'process form values.' These operations previously were part of the work
done by 'form' and 'submit.' The new setup is better for separation of
tasks, but more importantly fixes a bug that caused radio button fields to
throw validation errors because the field's validation was being run on
incompatible data.

requires running update.php.

- Removed extra hook_field_settings() parameter
- Corrected textarea/textfield confusion