#3 added possibility to enable/disable a FeatureSelectionChangedListener
#3 changed featureSelectionChanged() in MiPaRessortWidget
#3 added valueChanged_updateFeatures() in MiPaRessortWidget
#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 resolved merge conflict. Merged 'dev' into 'feature/2-undo-buttons'