This is a preparation to fix this bug: 184838 (the wrong keys are highlighted)

Reason: Instead of only labelling the new introduced keys, the most training files contain a description (basic keys instead of "asdfjklö")

This commit solves this problem on code base. A new xml tag has been introduced. One for the keys itself and one for the description. KTouch is compatible with actuall training files.
However the files need some work to have a expected behaviour.