Proposed change to the class hierarchy of openmrs objects

[teleivo (Ivo Ulrich)]

dear @wyclif, @dkayiwa and others should we discuss this at the design forum?

design forum 2016-09-12: for Order.dateChanged and changedBy

Dear @jthomas I would like to discuss issue and some quirks related to it that came up while working on the issue. Would be great to have @wyclif @dkayiwa and @darius if possible on related links/threads for background info: https://issues.openmrs.org/browse/TRUNK-4903 https://github.com/openmrs/openmrs-core/pull/1821 TRUNK-4730 - complete list of domain objects missing changed_by or date_changed Order.dateChanged, changedBy causing exception in ImmutableOrderInterceptor

I originally wanted to discuss https://issues.openmrs.org/browse/TRUNK-4903 but since this depends on this issue might be better to talk about this first.