KCM LookAndFeel : Remove unused Q_PROPERTIES, getter const, internal method...

KCM LookAndFeel : Remove unused Q_PROPERTIES, getter const, internal method private, typo in enum declaration

Summary: Clean up before moving LnF KCM to KConfigXT

Test Plan: Compile

Reviewers: #plasma, ervin, mart, bport

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D24819