Notification of string changes

Author: Tim Hunt
MDL-27430 qtype numerical put multiple-choice units back to radio buttons
It seems that people want to be able to use <sup> and <sub> here, which
makes sense, so we need to keep radio buttons for questions upgraded
from 2.0. The dropdown menu, however, is also nice, so keep that option
too for new questions.


http://git.moodle.org/gw?p=moodle.git;a=commit;h=8566369f630510f6453ff7edbe0fc2a40691b0e9
http://github.com/moodle/moodle/commit/8566369f630510f6453ff7edbe0fc2a40691b0e9

+ 2.1 en [unitselect,qtype_numerical]