TRUNK-4913 Concept.hbm.xml not-null on optional changedBy
Removed not-null="true"
Removed the not-null requirement from the many-to-many relationship on the changedBy column. I confirmed against a newly generated hbm.xml for Concept that this constraint doesn't belong. Build success, all tests passed. No new tests required.
Fixing: java.lang.IllegalAccessException: Class org.openmrs.web.filter.StartupFilter can not access a member of class org.openmrs.web.filter.startuperror.StartupErrorFilterModel with modifiers "protected static final" at org.openmrs.web.filter.StartupFilter.renderTemplate(StartupFilter.java:245)
(cherry picked from commit 1e7855244fb9adaaa94e83b425e0d8e610e45e65)
