Author: Petr Škoda
MDL-44824 add missing subplugin type names
http://git.moodle.org/gw?p=moodle.git;a=commit;h=aed0f5b78c8c99026f608ba35c4416411c5aa661
http://github.com/moodle/moodle/commit/aed0f5b78c8c99026f608ba35c4416411c5aa661
+ 2.7 en [subplugintype_ltisource,mod_lti]
+ 2.7 en [subplugintype_ltisource_plural,mod_lti]