Author: Jerome Mouneyrac
MDL-44228 add Atto sub-plugins admin table
http://git.moodle.org/gw?p=moodle.git;a=commit;h=6f0a16002a0d85188865209c84cfe9bc83edca23
http://github.com/moodle/moodle/commit/6f0a16002a0d85188865209c84cfe9bc83edca23
+ 2.7 en [subplugintype_atto_plural,editor_atto]