added toolbar groups' prefix policy to the ReleaseNotes.md
added toolbar groups' prefix policy to the ReleaseNotes.md

uhef/Oskari-Routing-frontend,uhef/Oskari-Routing-frontend,uhef/Oskari-Routing-frontend,uhef/Oskari-Routing-frontend,uhef/Oskari-Routing-frontend,uhef/Oskari-Routing-frontend