Adding support to Docker and requesting specific value

[Ultraxime]

The previous version was not compatible with docker as it was using modprobe, this new version uses iprout2 to leave to the host the ifb module's management. Testing may be done to see if it can now be used to shape the traffic on several interfaces (I didn't check)

In addition, I added the option allowing the user to specify the values they want instead of picking them at random given the network asked.

I also added a small example of interface shaping in Docker that can also be used to test if errant is working fine.