Author: Rossiani Wijaya
MDL-44032 Atto editor: add subscript and superscript plugins
http://git.moodle.org/gw?p=moodle.git;a=commit;h=39e2a67a53831edf002905e4c162264765f434ff
http://github.com/moodle/moodle/commit/39e2a67a53831edf002905e4c162264765f434ff
+ 2.7 en [pluginname,atto_subscript]
+ 2.7 en [pluginname,atto_superscript]