ENH: Add toolbar for the Extensions Manager and Error log

Fixes #3151

Co-authored-by: Jean-Christophe Fillion-Robin <jchris.fillionr@kitware.com>

From: Chrystel Juan <chrystel.juan@kitware.com>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22175 3bd1e089-480b-0410-8dfb-8563597acbee