Improve SvTreeListBox class

It is possible to set alternating rows. Expert Configuration
dialog use it.

Change-Id: Ie43a87ca05be73fdb345fa4866f31c2c36b7cdf1
Reviewed-on: https://gerrit.libreoffice.org/11663
Reviewed-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>
Tested-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>