Change default Dolphin toolbar layout

Summary:

Use a default toolbar layout that looks better and makes more sense for new users.

Test Plan: Open Dolphin (with the default toolbar)

Reviewers: Dolphin, VDG, ngraham, GB_2, elvisangelaccio

Reviewed By: Dolphin, VDG, ngraham, GB_2

Subscribers: iasensio, filipf, meven, elvisangelaccio, felixernst, GB_2, ndavis, ngraham, kfm-devel, VDG, Dolphin

Tags: Dolphin, VDG

Differential Revision: https://phabricator.kde.org/D23075