[API] Demo organizations and projects (Part 1)

With release the next release 0.12.0 demo organizations are introduced.
→ organization endpoints will change a bit. Mostly none breaking changes except additional fields are accepted

With the release 0.13.0 it’s no longer possible to create demo-projects (type FREE) in normal organizations (type standard). The creation will be limited to organizations of type demo.

Small change here. The second part lands in 0.14, not in 0.13. See the second post for details.