Refactor repository/project structure

Created by: elbenfreund

As a preparation for the upcoming addition of dedicated documentation and unit tests we need to refactor the repository layout.

Instead of equating the repository root with the extension root the following change should be implemented.

• Move extension code into separate directory
• Provide a simple makefile to handle packaging (currently done by build.sh).
• Provide licensing information
• Provide Contibution guideline