Create a rake task to run git-cop and document it.

Add a *How to write proper commit messages* section to the our
contributing file which include the git-cop current configuration.

We are using `dist` tag but is not in our contributing file.

foreman will start all services/daemons that you need for a
full fledged OBS. There is currently an issue with
thinking sphinx

https://github.com/pat/thinking-sphinx/issues/1049

That's why this is commented out. Nevertheless ts will
be started by clockwork.

MacOS and Windows do not necesarrily run on a case sensitive
filesystem but the backend source needs this.

Remove P0 label from the Contribution readme as it does not exist.

Closes https://github.com/openSUSE/open-build-service/issues/2146

memer -> member

Typo. cofiguration -> configuration

The password for Admin in CONTRIBUTING.md is opensuse and not buildservice.

We can't exec start_test_backend from inside script/ as this
clashes with https://github.com/rails/rails/pull/13528 somehow.

* Rename load_dev_backend to start_development_backend
* drop db:fixtures:obs