Contrail work

Contrail work.

Still working on below stuffs

1. Inline documentation
2. More complete spec tests
3. Pending vrouter part - this need working nova, so working on setting up nova. Vrouter code is already there so only some small changes would be required.
This way we can set neutron_ip specifically and if not set, the code will assume $::ipaddress of $interface set as default. 

Here instead of assuming the first ip address, for default, accepts a parameter for interface (which is defaults to eth0) and use ip address of that interface as default.

Please let me know what you think about it.