Add error handling during credentials onChange event so that the Scan Account feature does not activate if credentials are invalid

Because having to type the whole commands is a pain!

Right now, running terratag displays all log, even DEBUG logs.
We should let the user pick the log-level when running terratag

To avoid dependencies problems, we could provide a Dockerfile to allow the users to build the Terrible container by themself.
The container should include:

• Ansible
• Terraform
• Terraform Provider for Libvirt

And possibly also other things if necessary. The Travis pipeline could be inspirational for this issue.

See the TODO in bin/codedeploy/AfterInstall.sh