This commit adds superscript and subscript text formatting
options in formatting toolbar

Change-Id: Id6966eb11b71b269431a21f46bd7c597fdcdb08c
Reviewed-on: https://gerrit.libreoffice.org/35778Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>