Trunk-4444 Validate order overlap with scheduled date

Comments:
In Order.java:
          - getCalculatedStartDate and getCalculatedEndDate are kept public for future use.
          - Can rename getCalculatedEndDate and getCalculatedStartDate with better names (if any).
Renamed the tests. 
Also, each test checks vice versa overlap. i.e. order1.hasOverlappingScheduleWith(order2) has the same result as order2.hasOverlappingScheduleWith(order1). These opposite assertions are made in all tests. Let me know if still something is amiss.