Packet Trace CLI

Signed-off-by: Stephen Wong <s3wong@midokura.com>
Merge pull request #51 from s3wong/s3wong-trace1

Packet Trace CLI
CLI: Implement unlinking, DNS servers for dhcp, and other fixes.

Fixes MN-191, MN-192.

Also addresses the following issues:
-The -A flag now actually skips authentication.
-The set operation now supports object references.
-Support sending empty lists in API calls.

Signed-off-by: Brandon Berg <bberg@midokura.jp>