Cleanup stack artifacts

[mezarin]

Among other things these are the things that need to be addressed:

• Add copyright headers on files that need it (i.e. devfile.yaml, pom.xml, server.xml). This part intersects a bit with issue Convert stack artifacts in all related repos to ASL 2.0 license, and add copyright headers to java/xml #4
• Test and update documentation links and replace with correct ones (i.e. CONTRIBUTING.md)
• Properly define the contribution process and CLA (i.e. CONTRIBUTING.md) and licenses.
• Add an odo test case in test/stack-test-inner-loop.sh