Backport commit 04b70e28a1 from master to 2.4.x

This patch was added to 2.3.x and master just before 2.4.0 was released and we postponed backporting to 2.4.x for after the 2.4 release.
The patch lets user/plugin defined WFS transaction properties to be passed down to the geotools transaction that ultimately handles the WFS transaction for plugins/datastore implementations that can make use of them.