Move General settings to the top

Summary: KDE apps generally (ha ha) have their General page at the top of the list, so it's the first thing the user sees when they open the Settings window, but Dolphin is an exception. It puts the General page last! This patch makes Dolphin consistent with other KDE apps by moving the General page up to the top.

Test Plan:

Reviewers: Dolphin, KDE Applications, elvisangelaccio, ltoscano

Reviewed By: elvisangelaccio, ltoscano

Subscribers: kde-doc-english, ltoscano, elvisangelaccio, kfm-devel

Tags: Dolphin, Documentation

Differential Revision: https://phabricator.kde.org/D13595