On restart do not update end time silently

[ckunki]

This applies especially after user has clicked "stop working for today".

Proposal: ask user for confirmation before updating end time.

WhiteRabbit shows a dialog in this case with three options:

• Stop working for today
• Skip interruption
• Add interruption

The naming of these buttons should be improved for better usability:

• Register end-of-work for today
• Ignore interruption
• Register interruption