Add LICENSE

LICENSE

+--------------------------------------------------
+Python-Fortran binding benchmark
+--------------------------------------------------
+
+This project is distributed under LGPL. In agreement with the
+Intergovernmental Convention of the ILL, this software cannot be used
+in military applications.
+
+Copyright (C) 2019       Institut Laue-Langevin (ILL), Grenoble, FRANCE
+                         European Spallation Source (ESS), Lund, SWEDEN
+
+This library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Lesser General Public
+License as published by the Free Software Foundation; either
+version 3.0 of the License, or (at your option) any later version.
+
+This library 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
+Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public
+License along with this library; if not, see <http://www.gnu.org/licenses/>.
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