update licence details

Author: yomguy

doc/source/copyright.rst

@@ -16,12 +16,12 @@ License
 
 TimeSide is free software: you can redistribute it and/or modify
 it under the terms of the GNU Affero General Public License as published by
-the Free Software Foundation, either version 2 of the License, or
+the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.
 
 TimeSide 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 Affero General Public License for more details.
 
-See LICENSE for more details.
+Read the LICENSE.txt file for more details.