Add end-indicator decision tree and change session settings

[robbertbos]

Description

1. The current decision tree does not contain a button indicating that the end has been reached and the results can be saved.
   Part of the work is agreeing how exactly this should be reflected in the decision tree.

2. It is also necessary to revise the storage structure. Currently, the browser remembers history, so that when the decision tree is reopened, previously entered information is still visible. The proposal is to remember data by ‘session’ rather than by browser.

Sketch of the design:

Implementation Notes

• Set local storage to remember data by ‘session’ rather than by browser
• Add 'Sluit' button to conclusion page. The Sluit button closes the decision tree modal/page. Saving the results is out of scope for now.
• Also change AMT to use the sessionstorage for the retrieval of the labels compared to localstorage right now

[laurensWe]

Waiting for feedback from heitske