MDL-25660 recreate all workshop calendar events

Due to complex workshop upgrade path from 1.9 and missing calendar events
support in 2.x, the only safe way to get rid of potentially invalid
calendar events (such as those reported in MDL-26687) is to remove all
current workshop events and recreate them from scratch.

mod/workshop/version.php

@@ -25,7 +25,7 @@
 
 defined('MOODLE_INTERNAL') || die();
 
-$module->version   = 2012030700;       // The current module version (Date: YYYYMMDDXX)
+$module->version   = 2012041300;       // The current module version (Date: YYYYMMDDXX)
 $module->requires  = 2012030100.04;    // Requires this Moodle version
 $module->component = 'mod_workshop';   // Full name of the plugin (used for diagnostics)
 $module->cron      = 0;