TRUNK-3840: Refactoring code to display retired set member

https://issues.openmrs.org/browse/TRUNK-3840

Refactored concept.jsp; removed repeated code.
Add code to ConceptSet.java to factor in retired concepts while sorting
Added unit test for new behavior

Updated concept.jsp view and ConceptFormController
This test is supposed to be in ConceptSetTest because it testing code in ConceptSet an not Concept class, you can use https://wiki.openmrs.org/x/FhIz to easily achieve such conventions