ewaol-config/kas-ci-build: Build script improvements

* Allow the container's network mode to be set via an input argument.
* Validate that the input kas config files for each target can be found.
* Allow the container engine, image, and image version to be set via input
  arguments.
* Ensure the executed container engine subprocess is stopped on a keyboard
  interrupt or terminate signal to avoid dangling containers.
* More clearly log where artifacts were deployed, and reduce log verbosity.
* Include images in the artifacts deployment.
* Include 'pseudo' log files in the log-artifacts deployment.
* Allow for a log file to be given as an input argument, which will log the
  output of the script (duplicating the terminal output).
* If a log-file is provided then reduce the output verbosity to print only an
  important subset of messages to the terminal.
* Allow for container engine volumes to be defined using relative paths in the
  input arguments.
* Update the script to be PEP8 compliant.

Issue-Id: SCM-2619
Signed-off-by: Richard Neill <richard.neill@arm.com>
Signed-off-by: Diego Sueiro <diego.sueiro@arm.com>
Change-Id: If6bf65270480b9562dc08c6c03bcf4621c4e5566