Add support for new tables to support external devices

Initial changes to support managing of external devices. Following tables
are added,

Physical-Device :
Table for physical-router defined in configuration

Physical-Interface :
Physical-Interface on physical-router. Interface can be local when its
attached to local vrouter. Interface is remote when its attached to
an external physical-device

Logical-Interface:
Multiple Logical interface interfaces can be created over an phyiscal-interface.
Currently agent supports only vlan-tag based Logical-Interfaces

Physical-Device-Vn:
Table of physical-device to virtual-network. The table is built from following
configuration
<physical-router> - <physical-interface> - <logical-interface> - <VMI> - <VN>

Added XML based UT framework for new tables

Change-Id: I313d89ca944e46b02ac0639f26807b1ba2047ae8
Merge "Add support for new tables to support external devices"