Add a reload button

This PR adds a button to close the current project and regenerate all figures. This will also close the handles to the datasets on disk, so it is useful when your data on the disk changed, but you do not want to click on everything to make new plots.

• Tests added (for all bug fixes or enhancements)
• Tests passed (for all non-documentation changes)
• Fully documented, including CHANGELOG.rst for all changes