+ Added registy entry to store icon size
+ Added UI to change settings: Tools -> Options... -> View
+ Loading last settings in the SidebarToolBox
+ Settings update listener

Update icon code from: framework/source/uielement/toolbarmanager.cxx

Change-Id: I1d713c50fccfc19e1c8ea82eba68556ddb76cd3c
Reviewed-on: https://gerrit.libreoffice.org/26362Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Samuel Mehrbrodt <Samuel.Mehrbrodt@cib.de>