process_posted yield field instead of field's name

proper field's role handling: may be 'subject' / 'object' *in case of entity's relation*, but None in other case. So you should correctly specify it to field_by_name

form_add_hidden -> add_hidden form_needs_multipart -> needs_multipart

substitute _render_attrs by values_and_attributes method, keeping bw compat

replace form_field_[encoding|vocabulary] methods on form by encoding|vocabylary(form) methods on fields

refactor vocabulary handling to avoid having to define methods on form objects, use .choices instead even for non final relations. Details: * deprecated support of <role>_<relation>_vocabulary methods on forms * new utility functions for relations vocabulary * most logic now on the RelationField class

cleanup

refactor form field value handling, to get a nicer api and an easier algorithm to get field's value Details: * new .typed_value / .display_value on fields * droped form_field_value on form * .value attribute of field instead of .initial * nicer field's __init__, allowing to give a lambda as value's value