Move settings-related member variables into own class
Move settings-related member variables into own class

Idea is to keep amount of state low, for any given class.
MaliitKeyboard::InputMethod is a candidate that easily attracts new member
variables so constant clean ups are necessary.

RevBy: TrustMe

This work was done by Openismus GmbH for Canonical Ltd

maliit/plugins,KDE/plasma-maliit-plugins,RHawkeyed/plugins,develersrl/maliit-demo-qml,RHawkeyed/plugins,maliit/plugins,KDE/plasma-maliit-plugins,KDE/plasma-maliit-plugins,KDE/plasma-maliit-plugins,develersrl/maliit-demo-qml,RHawkeyed/plugins,develersrl/maliit-demo-qml,RHawkeyed/plugins,develersrl/maliit-demo-qml,maliit/plugins,RHawkeyed/plugins,maliit/plugins