Moved all getters from Element to ElementHelpers. Existing ElementHelpers getters `get_namespace` and `get_local_name` were replaced by `namespace` and `local_name`. Callers were updated accordingly. Also the getters are no longer inlined. 3 of the getters needed to be added to RawLayoutElementHelpers as well, to accomodate existing calls directly from Element objects. Source-Repo: https://github.com/servo/servo Source-Revision: 9541dcdee271d83834af12c756932697ab0ef5dc