License for extension/images/icon_*.png

  This work is licenced under the Creative Commons Attribution-Share Alike 3.0
  United States License. To view a copy of this license, visit
  http://creativecommons.org/licenses/by-sa/3.0/ or send a letter to Creative
  Commons, PO Box 1866, Mountain View, CA 94042, USA.

  Created by
  * Gabor Karsay <gabor.karsay@gmx.at>
  using and modifying artwork from the
  * GNOME Project, http://www.gnome.org

License for extension/images/*chainframes.png,
            extension/images/*timefield.png:

  This work is licenced 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.

  Copyright 2018 by Rizal Muttaqin <riz_17_oke@yahoo.co.id>
  https://github.com/rizmut/libreoffice-style-elementary/blob/master/images_elementary/cmd/32/chainframes.png