Author: David Mudrak
MDL-26099 validate the phases open dates and deadlines
http://git.moodle.org/gw?p=moodle.git;a=commit;h=df558765a43df1593113ecebd2faa8fb24bbad5b
http://github.com/moodle/moodle/commit/df558765a43df1593113ecebd2faa8fb24bbad5b
+ 2.3 en [assessmentendbeforestart,mod_workshop]
+ 2.3 en [phasesoverlap,mod_workshop]
+ 2.3 en [submissionendbeforestart,mod_workshop]