Scenario Manager: auto reload on changes from disk

Currently the scenario manager saves changes from the gui on the disk disregarding any changes made to the file on disk. Additionally, changes done to an application of a scenario will lead to all scenarios being stored to disk. That is, modifying any two (or more) applications from the same scenario from two different GUIs will lead to lost data.

Implement a feature to reload changes automatically when the underlying file is changed.