Author: Eloy Lafuente (stronk7)
MDL-28036 quiz - add some missing (reports) lang strings
http://git.moodle.org/gw?p=moodle.git;a=commit;h=8b95f430b55d589997fbad82d0115a740cc428e3
http://github.com/moodle/moodle/commit/8b95f430b55d589997fbad82d0115a740cc428e3
+ 2.1 en [subplugintype_quiz,mod_quiz]
+ 2.1 en [subplugintype_quiz_plural,mod_quiz]
+ 2.1 en [pluginname,quiz_grading]
+ 2.1 en [pluginname,quiz_overview]
+ 2.1 en [pluginname,quiz_responses]
+ 2.1 en [pluginname,quiz_statistics]