Create docker image to run w3af inside

[andresriancho]

Create docker image to run w3af inside which will speedup the setup phase. Remember that we have to re-compile python now to have support for some of our tools.

TODO

• Create a Dockerfile in collector/examples/w3af based on the w3af docker image but installing all the other things I need for profiling
• Also update the ami to point to one that already has docker installed:

main:
  ami: ami-48eb2f20

• Create a script to run w3af inside docker and save the profiling output to a place where I can easily download afterwards