#3 added possibility to enable/disable a FeatureSelectionChangedListener
#3 changed featureSelectionChanged() in BaumRessortWidget
#3 added valueChanged_updateFeatures() in BaumRessortWidget
#3 if the only selected element has no feature, unselect all features in map
Merge branch 'bug/3-select-feature-select-table' into dev
#2 Merge conflict resolved. Merged 'dev' into 'feature/2-undo-buttons'