+ added scenario reference to unitModel in order to achieve the former
+ added hasSource() and hasTarget() to connectionModel
! in contextInfoController: fixed bug in saving chosen parameter (was overridden due to reference instead of copy)
# "speichern" button now again saves scenario JSON instead of a-box (as before)
+ added workaround for stringifying unit model which contains circularity (reference to scenario) on downloading scenario JSON

+ added connectsUnit() to connectionModel, which checks if the connection leads to/from the given unit
+ added removal of attached connections to removeUnit() in scenarioModel: connections leading to/from a deleted unit will be deleted from model, too
# removeConnection() in scenarioModel now accepts only the ID of a connection as parameter (instead of the entire connection)
- removed deleteUnitFromModel() from unitModel
+ added removeUnitFromScenario() to unitController, comprising all necessary function calls for removing a unit from view and model
# merged similar but distributed unit deletion functionality from tab and modal window into removeUnitFromScenario() call; now all use the same functionality
+ added check for existence of a unit model to its click event handler: prevents errors when units are added and clicked but not named yet
+ added check for scenario name availability to newScenarioModal....: alert if entered name for new scenario is already taken
! fixed (really stupid, really) unit deletion bug (i.e. not happening): added "#" to delete unit button $-selectors
+ added TODO to loadScenario() in authorSystemController: the whole thing is stale and just won't work

# moved event handlers for connections from canvasController to relationTabController
# moved initUnitEventHandlers() from canvasController to unitController
# moved chooseMetaIcon() from unitController to formatSelections
+ added optional index parameter to addContextInfo() in unitModel
+ added getItemByID() to contextInfoListModel
# started correcting German umlauts in dictionaries
# changed data structure of array_multiSelectionContextInfos:
   1. "id" is now context ID, "text" its translation;
   2. new items now get pushed to the end of the array, changed items stay where they are
# changed changeColorMultiContextInfos() into formatMultiContextInfosElements()
TODO: editing items in multi selection does not work as it should (see latter changes)