This commit renames the image-type field to image-variant
in the test cases files.

It also updates the parser, renderer code, test_case template
and unittests files in order to use the new name.

Signed-off-by: Luis Araujo <luis.araujo@collabora.co.uk>

This commit applies the required changes to the test cases so
they can be executed in LAVA.

The change consists in adding the `git-repos` directive so they
can fetch the tests scripts from LAVA.

This is the group 0 in a serie of commits to integrate all the
tests into LAVA.

Signed-off-by: Luis Araujo <luis.araujo@collabora.co.uk>

Signed-off-by: Luis Araujo <luis.araujo@collabora.co.uk>

- Update the README listing existing macros and how to
  use the renderer.
- Rename the main program to render-test-case
- Rename the tc directory to tests-cases

Signed-off-by: Luis Araujo <luis.araujo@collabora.co.uk>

- Add a new post-condition section.
- Add a new macro to install packages for automated tests.
- Slightly change the way the function to parse lists work. Now
  only the run.steps section will be treated different from
  other sections.
- Apply syntax changes to the already ported test cases.
- Add new ported test cases.
- Update the README explaining a rule for the formatter.

Signed-off-by: Luis Araujo <luis.araujo@collabora.co.uk>

Signed-off-by: Luis Araujo <luis.araujo@collabora.co.uk>