Confirm Before Closing Part Editor

[leokrebber]

When creating or editing a part, accidentally closing the tab or clicking on a category will immediately discard all changes in the editor.

The editor should ask whether you want to discard the changes before closing the tab.

Can be reproduced by:

1. Pressing on the "Create new part" button
2. Entering info for a part
3. Closing the tab or clicking on a category
4. Having the editor discard all changes without warning