Tests: update the stub code to match the current binary LunaNext module.

 * Add a Compositor Item
 * For consistency with its usage and content, rename LunaNextStub.js to SettingsStub.js

Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>
Merge pull request #1 from webOS-ports/tofe/teststub-update

Tests: update the stub code to match the current binary LunaNext module.