Only save scenario slider setting changes until user clicks "Finish editing"

[mabijkerk]

When a user opens a MYC scenario and goes to slider settings to edit the sliders of one of the scenarios, the changes are immediately saved. For example, if I open a new MYC session, set the share of electric cars to 100% for one of the years and then return to the homepage of the ETM, without clicking "Finish editing" in the bottom right. When I then go back to the MYC tool and resume the session, the share of 100% electric cars is present in the scenario.

Would it be an option to only actually save changes when a user hits "Finish editing"? This would improve the user flow, as it would allow users to play around with sliders before conscientiously making the changes definite.

[mabijkerk]

Notifying @thomas-qah in relation to #36