_search overwritten in res_company to allow user to change of company among its allowed companies is not usefull anymore, name_search is now the method to overwrite.
moreover, widget selection replaced by options no_create in user preferenes view, to allow typing in the many2one(for searching purpose) without having the option to create a new company or edit.
bzr revid: dle@openerp.com-20140304175231-ojhzqecrdkjg2w52