Add vppctl as a simple cli interface to vpp

Add vppctl as a simple cli interface to vpp

This patch provides a pretty simple hack on top
of vpe_api_test to give users a cli interface
to vpp.

Example:

sudo vppctl show api client
sudo vppctl show int

It has the advantage that users can use bash shell scripting
and history with it.

Change-Id: I621dd8e29269e14a83b4887f20adcfbe5f946b99
Signed-off-by: Ed Warnicke <eaw@cisco.com>