Update copyrights in files.

gradle.properties

@@ -1,17 +1,20 @@
 #
-# Copyright (C) 2016 Phillip Hsu
+# Copyright 2017 Phillip Hsu
 #
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
+# This file is part of ClockPlus.
 #
-#      http://www.apache.org/licenses/LICENSE-2.0
+# ClockPlus 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.
 #
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
+# ClockPlus 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 ClockPlus.  If not, see <http://www.gnu.org/licenses/>.
 #
 
 # Project-wide Gradle settings.