Merge branch 'feature/gitlab-readable-contribution-and-licensing-guide' into 'master'

GitLab readable contribution guide, license and README

Adding the `.md` extension enables rendering of the files, which is much nicer.

Also ported the contribution guide from the User Wiki.

Renamed COPYING to LICENSE.md because that is the name that GitLab looks for to display it nicely on the project starting page.

If this one is accepted, I will do the same for the other core modules.

See merge request !5
(cherry picked from commit 633391ff)

Signed-off-by: Steffen Müthing <muething@dune-project.org>

CONTRIBUTING.md

+Contributing to the Dune Core Modules
+=====================================
+
+You've squashed an annoying bug or implemented a nifty new feature in DUNE?
+And you're willing to share your improvements with the community? This page
+explains how to get those changes to us and what to take care of.
+
+Take a look at the DUNE coding style
+------------------------------------
+
+Your work will enjoy much smoother sailing if you take a look at the Coding
+Style and try to stick to it with your changes. We understand that everyone
+has their personal preferences and that there is no such thing as the *right*
+coding style (in the end, it's a matter of taste), but DUNE is a pretty large
+project, and a consistent way of doing things really helps a lot when trying
+to find your way around a body of code as big as DUNE.
+
+Make sure to install the Whitespace Hook before starting to work, because
+our repositories enforce certain rules about whitespace and will not accept
+commits that violate those rules. And a developer will be much more motivated
+to merge your patch if doing so does not involve fixing a bunch of tab-based
+indentations that you inadvertently added as part of your changes
+
+Use Git to your advantage
+-------------------------
+
+We know, Git can be a bit daunting at first, but trust us, it's really worth
+investing half an hour to learn the basics! Even though you don't have any
+commit rights to the DUNE repositories, Git still allows you to create local
+commits on your machine, avoiding the usual ugly business of creating backup
+copies, copying around code in files, commenting and uncommenting variants etc.
+And when you're done and send the changes to us, we can simply import those
+commits into our repositories. That saves a lot of time and when your changes
+can be applied in five minutes using two or three commands, chances are a
+developer will much more easily find the time to do so. Git is really popular,
+so there are tons of tutorials all over the web. Here are some pointers:
+
+* http://try.github.io/ is a very quick, hands-down introduction
+  to Git that allows you to try out Git directly in your browser.
+  Requires a GitHub account to continue at some point, though.
+* http://git-scm.com/book is a very well-written and detailed resource
+  for all things Git. Chapter 2 is a great introduction to Git that also explains
+  a little bit how Git works, which really helps to reduce the number of
+  *WTF just happened?* moments. ;-)
+* http://eagain.net/articles/git-for-computer-scientists/ is a short and
+  sweet explanation of what Git does at a fundamental level - just the thing for
+  scientists! ;-)
+* http://git-scm.com/doc/ext is a collection of both introductory and
+  more in-depth Git resources.
+
+Whatever you do, make sure to set your Git identity so that the commits tell us who authored them!
+
+Getting the changes to us
+-------------------------
+
+You should get your changes to us in the following way:
+* Get an account for [our GitLab instance](htpp://gitlab.dune-project.org).
+* Fork the core module that you want to contribute to, just
+  as you would do on GitHub.
+* Push your changes to your fork on some branch.
+* Open a merge request using the branch you pushed your changes
+  to as the source branch and the master of the core module repository
+  as the target branch. GitLab will usually ask you about opening
+  a merge request if you browse it right after pushing to some branch.
+* Follow the discussion on the merge request to see what improvements
+  should be done to the branch before merging.
+
+If you have any questions or complaints about this workflow of
+contributing to Dune, please rant on the
+[dune-devel mailing list](mailto:dune-devel@dune-project.org).

COPYING

+LICENSE.md
\ No newline at end of file