Change default Dolphin toolbar layout

Summary:
{F7205836}

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