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).
I guess it is fine to leave method here to keep it testable, but i would make the javadocs clear that it compare dates only if you want to ignore things like voided, care setting, action etc.