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).
3rd test does it- "@should return true if this order and other order have same dates". Same order is preserved in test file.
I have refactored statements of test cases a bit. Let me know if you find any problem in understanding scenarios.