Code refactoring and added new checks

Code refactoring and added new checks

1. Divided code into subclasses
2. Before deleting the interface now method checks if:
   --interface exists
   --if yes, then change admin state to out of service
   --if change of state successful then delete
3. Before creating interface now the method checks if:
   --if interface with same name in service exists then donot create
     new
   --if exists but state not in service then create new
   --if does not exist then create new interface with state in service
4. Before deleting a cross connect check if it exists, if not
   then do not proceed.
5. Created new class CrossConnect.java with methods:
   --getCrossConnect()
   --postCrossConnect()
   --deleteCrossConnect()
   --setPowerLevel()
   --getConnectionPortTrail()
6. Created new class OpenRoadmInerface.java with methods/attributes
   common to all interface irrespective to their type:
   --getIntfBuilder()
   --postInterface()
   --getInterface()
   --deleteInterface()
7. Added child classes OpenRoadmOdu4Interface.java,
   OpenRoadmOchInterface.java,OpenRoadmOtu4Interface.java
8. Added check for nodeType mandatory field.
9. Added checks for null value in data change notification
   when a device is disconnected.

Change-Id: Id775e36a8db0d14a11147e23414df4b07d1d6910
Signed-off-by: Dhruv Bhardwaj <db929a@att.com>