[views/table] parametrize table view co-classes (closes #1947472)

[cwproperties] refactor properties form to make it partly overrideable easily (closes #1936782) also fix some pitfalls on the way: * shouldn't capitalize labels, this has to be done in translation files as desired * form_row in CWProperties form didn't return subform as its parent class

[entity] rename Entity._rest_attr_info into cw_rest_attr_info (closes #1942759)