Proposals for changes in contribution principles

See:
  - https://github.com/lra/mackup/pull/405
  - https://github.com/lra/mackup/pull/153
  - https://github.com/lra/mackup/pull/175
  - https://github.com/lra/mackup/pull/127
Merge pull request #406 from kfinlay/patch-2

Proposals for changes in contribution principles