A few small performance improvements
Fix cell merging issues, add colours and orientation, hide header and footer
Add basic borders (no colour or weight)
Add workaround for cell shading patterns
Switch back to NetOffice interop
Basic panel selection and file dialog
Add XAML for choosing Excel workbook and worksheet
Invoke panel selection and worksheet dialog from command
Basic schedule import extensible storage schema
Add XAML for managing linked schedules
Make manage schedule links UI look nicer
Clean up a little bit in ScheduleImport