Added license text to source files

nw/gui/theme.py

@@ -8,6 +8,21 @@
  File History:
  Created: 2019-05-18 [0.1.3]
 
+ This file is a part of novelWriter
+ Copyright 2020, Veronica Berglyd Olsen
+
+ 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 https://www.gnu.org/licenses/.
 """
 
 import logging