HUMAN: improve the look of the default icon set used in ubuntu

Change-Id: I5de4bce2632a94d0a94b4d8212525e9a35790ca0
Reviewed-on: https://gerrit.libreoffice.org/13689
Reviewed-by: Yousuf Philips <philipz85@hotmail.com>
Tested-by: Yousuf Philips <philipz85@hotmail.com>