Added code for PhysicalPort, LogicalSwitch

1. Added PhysicalPortUpdate and PhysicalPortRemove
2. Added LogicalSwitchUpdate and LogicalSwitchRemove
With these changes physical-port and logical-switch changes on device are
reflected in OperationalDS.

Patchset2:
1. Rebase
2. Add VlanBindings to OperationalDataStore
3. Use env vars for IPs in postman collection
4. Fixed a bug in postman collection

Change-Id: Ic1b3d0e15088db6d81316ad88c2db5299a9c9be0
Signed-off-by: Vishal Thapar <vishal.thapar@ericsson.com>