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 have removed this method. 
- Only "hasOverlappingScheduleWith" remains that has the responsibility of just checking overlapping schedule on the basis of date.
- I should make changes to check if otherOrder is null and return false in that case.
- It doesn't care about caresetting as I am assuming it would be called to check overlap after fetching orders belonging to certain care setting (in conjunction with getActiveOrders that takes care of caresetting).
About different order actions
- Should we take care of Discontinued and Revised orders separately? They set the stoppedDate (after discontinuing/revision) of the order which is the date logic compares against.