Add cancel option to ClearAllData request

[CodeCricut]

When a ClearAllData command is issued, the user may want to cancel the command before it has completed. To fulfill this, these basic steps need to be taken:

• add UI for cancelling the command
• use a cancellation token within the ClearAllDataHandler command handler
• in the case of a cancellation, the changes should not be saved to the repositories within the Handle method of the command handler