Author: Frederic Massart
MDL-51506 tool_lp: Implementing validation in the models
http://git.moodle.org/gw?p=moodle.git;a=commit;h=dee2fb575e853e52e2c96c7c58c2185a1e4154e3
http://github.com/moodle/moodle/commit/dee2fb575e853e52e2c96c7c58c2185a1e4154e3
+ 3.1 en [invalidpersistent,tool_lp]