file header for AmrPoissonSolver class

src/Solvers/AmrPoissonSolver.h

+//
+// Class AmrPoissonSolver
+//   Base class of AMR poisson solvers.
+//
+// Copyright (c) 2016 - 2020, Matthias Frey, Paul Scherrer Institut, Villigen PSI, Switzerland
+// All rights reserved
+//
+// Implemented as part of the PhD thesis
+// "Precise Simulations of Multibunches in High Intensity Cyclotrons"
+//
+// This file is part of OPAL.
+//
+// OPAL 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.
+//
+// You should have received a copy of the GNU General Public License
+// along with OPAL. If not, see <https://www.gnu.org/licenses/>.
+//
+
 #ifndef AMR_POISSON_SOLVER_H_
 #define AMR_POISSON_SOLVER_H_