This commit introduces a number containerization options useful for
building and testing the SCP-firmware project without requiring that
developers manually install the prerequisites.

The core container configuration is given by `docker/Dockerfile`, which
creates an Ubuntu 20.04 image including any tools required to build and
test the project.

This commit also adds a Visual Studio Code development container
configuration and a Vagrant configuration for bringing up a VM-like
development environment.

Change-Id: Ibdc8e8e1fd007ecdfa822cf14e156b9bb1a5f2be
Signed-off-by: Chris Kay <chris.kay@arm.com>
Signed-off-by: Joel Goddard <joel.goddard@arm.com>
Signed-off-by: Girish Pathak <girish.pathak@arm.com>