Add button that imports evaluation data from local storage

[teodorachiosa]

I really needed this feature or something similar implemented ASAP (#56).
I wasn't able to make it automatically load the content like how the ATAG tool works, so I added a button instead. If anyone has a better implementation - closer to how ATAG works, feel free to ignore this PR and create a new PR.

Changes:

• Updated the tool so that any changes to the report are saved to the browser's local storage
• Added a button on the Overview page that allows you to open the data from the local storage (almost identical functionality to the "Open report" button, but the content is loaded from local storage, not from a file).