Contribution: Pull Request Descriptions

- pull request descriptions are, besides issues, an extremely
  important reference for the change log
- one maintainer for coordination usually works out for small
  changes, one should try to let other developers have a second
  look, too
- bigger changes should at least try to get two persons in the review
Correct Typos, Thx @f-schmitt-zih
Merge pull request #524 from ax3l/doc-pullReqDescription

Contribution: Pull Request Descriptions