Revert unsaved changes button resets the entire scenario instead

[kaskranenburgQ]

The 'Revert unsaved changes' button implies that any unsaved changes that are have been mode to the scenario will be removed and that the scenario go back to the state at the time of the latest save.

Currently, this is not the case. While pressing the button, the scenario will reset all the changes that have been made to the scenario.

This effectively means that the scenario will return to a blank scenario.

Update:
With #4403, we partly solved this issue.
reverting unsaved changes will only work when:

1. You save your (non-blank) scenario.
2. Open a different or new scenario
3. Open your saved scenario.
4. Make changes
5. Press the 'revert unsaved changes' button.

If you don't open a different scenario in between, the revert unsaved changes button will revert to a blank scenario since your sessionID will not have changed, causing etmodel to think there is no scenario to revert to.

To fix this @mabijkerk suggests the following:

perhaps we should force a new SessionID anytime you save a version?

[kaskranenburgQ]

Some first investigation by @noracato led that this issue could be fixed by the removal of the following line of code:

etmodel/app/models/setting.rb

Line 100 in ec9a0e7

self.preset_scenario_id = nil # to go back to a blank slate scenario

I could not properly test this yet, due to some issues with scenario saving locally.