Added GPL copyright notice

Added the required copyright notice under the GPL license, this will need to be added to every source file.

An easy way to do that is the following:

1. In eclipse, go to `Window` -> `Preferences` -> `Java` -> `Code Style` -> `Code Templates`
2. Under `Code` edit `New Java File` to contain the following:
  ```
  ${filecomment}

  ${package_declaration}

  ${type_declaration}
  ```
3. Under `Comments` edit `Files` to contain the following:
  ```
/*
 * This file is part of CrafTech.
 *
 *  CrafTech 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.

 *  CrafTech 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 CrafTech.  If not, see <http://www.gnu.org/licenses/>. 
 */
  ```
This will automatically insert the copyright notice into every new file created