Summary:
All 3 comic's configuration windows (General, Appearance, Advanced) have been ported to QQC2 and Kirigami.FormLayout. Other changes include:

- the icon for the Appearance category is now consistent this with the icon used for this category elsewhere
- improving the wording of options
- removing the sections in Appearance and Advanced tabs
- making it explicit that the navigation buttons can always be shown or only on hover

Test Plan:
Before (General):
{F6696131}

After (General):
{F6700511}

Before (Appearance):
{F6696133}

After (Appearance):
{F6700512}

Before (Advanced):
{F6696136}

After (Advanced):
{F6700515}

Reviewers: rooty, ngraham, #vdg, #plasma

Reviewed By: ngraham, #vdg

Subscribers: abetts, mart, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D19802