Refactor VpnManager module.
+ Refactoring VpnManager to support subnet routing for hidden IPv6
addresses.
+ Moved all IP learning classes to package org.opendaylight.netvirt
.vpnmanager.iplearn.
+ Renamed few classes to Ip*** instead of Arp*** to keep it common for
both IPv4 and IPv6.
+ Refactored code in iplearn package to handle both IPv4 and IPv6.
+ Kept placeholders (TODO's) for supporting IPv6 subnet routing for
hidden IPs.
JIRA: NETVIRT-1213
Change-Id: I7f2c7968d92d61b4d3e1d8a1d858df34368344e8
Signed-off-by: Somashekar Byrappa <somashekar.b@altencalsoftlabs.com>