Document branching

• Releases:
  • x.y.z-release
    • x.y.z.a-release for bug fixes
  • x.y-release for API changes
• Development
  • x.y-development for ongoing development of that line

New Development branches started before the release branch, and the release branch is forked from the corresponding development branch.

All others are feature/topic branches and subject to purging if not active.