[JBPM-2958] Timer should refer to the business calendar used at the time of creation

If your JBoss BPM installation employs multiple business calendar property files and you had set a timer to repeat, the job executor would not know which business calendar properties file was in use when the timer was created. This update introduces a new column called CALENDARRESOURCE_ to the JBPM_JOB table that store the name of the business calendar properties resource used to create a timer. To avoid forcing unaffected customers to create the aforementioned column manually, this update is disabled by default. In order to enable it, replace the org/jbpm/job/Timer.hbm.xml mapping resource with org/jbpm/job/Timer.calendar.hbm.xml in the Hibernate configuration, after you have created the column.