Add separate copyright notice. Update README.md

COPYING.md

+# Copyright Notice
+
+    DORiE – The DUNE Operated Richards Equation Solving Environment
+    Copyright (C) 2019  DORiE Developers
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+A copy of the [GNU General Public License](LICENSE) is distributed with the
+source code of this program.
+
+## Copyright Holders
+
+The copyright holders of DORiE are referred to as *DORiE Developers* in the
+respective copyright notices.
+
+DORiE has been developed by (in alphabetical order)
+
+* Dion Häfner
+* Ole Klein
+* Santiago Ospina De Los Ríos
+* Lukas Riedel
+* Felix Riexinger

README.md

@@ -7,6 +7,9 @@ The suite encapsulates a documentation and various tools for program setup, prog
 
 DORiE is developed and maintained by the [DORiE Developers](mailto:dorieteam@iup.uni-heidelberg.de) of the [TS-CCEES](http://ts.iup.uni-heidelberg.de/) research group at [IUP Heidelberg](http://www.iup.uni-heidelberg.de/), supervised by [Kurt Roth](http://ts.iup.uni-heidelberg.de/people/prof-dr-kurt-roth/), in collaboration with [Ole Klein](https://conan.iwr.uni-heidelberg.de/people/oklein/) and the [Scientific Computing Group](https://conan.iwr.uni-heidelberg.de/) of [IWR Heidelberg](https://typo.iwr.uni-heidelberg.de/home/).
 
+DORiE is licensed under the [GNU General Public License v3.0](LICENSE).
+For the copyright notice and the list of copyright holders,
+see [COPYING](COPYING).
 
 # Installation Instructions