[kde-doc-english] System Settings Categories" needs hyperlinks

[Krzysztof Żelechowski]

The page "System Settings Categories" [1] needs hyperlinks to the documentation of the configuration modules.  For example, Application Appearance [2].

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[1] <URL:http://docs.kde.org/stable/en/kdebase-workspace/systemsettings/general.html>
[2] <URL:http://docs.kde.org/stable/en/kdebase-workspace/kcontrol/kcmstyle/index.html>