Added support for compositor tests. Compositor tests can be added, executed and viewed in a similar way to cycles
and other render engines tests.
Running test:
`ctest -R compositor`
Updating test:
`BLENDER_TEST_UPDATE=1 ctest -R compositor`
Viewing test results:
typically saved under `build_folder/tests/compositor/report.html`
Reviewed By: jbakker
Differential Revision: https://developer.blender.org/D6334