fixed initialization of fields
let subclasses use a different message bundle
init() must be called before initDefault()
single attribute group now shrinks width and height according to parent
if not valid and no changes then display validation error.
don’t display schema selector if only one available
add property to allow visiting a group (e.g. if it is used as an attribute  model)
improve validation
added live model updates to rich text editor
changed formatting
formatting
improved lay outing to also grow sideways
fixed lint error
added getOldValue
create and editMulti with empty schemas array is possible, too.
add parameter for initalValue to Opener.createSingle
fix validateRecursively (did not compute children errors)
fix resetMetaRecursively
MultiGroup is visited by default - especially useful for validation.
fix test. initDefault is not called, if init was never called
removed console.lod and TODO