Add export feature for charts

[jochenwezel]

Feature request

Excel charts must be exportable

Considerations

• Export features are limited by engine and OS platform

ToDos

• MS Excel engine
  • Windows platform
    • should work
  • Non-windows platform
    • NOT supported by engine
• FreeSpireXls engine
  • Windows platform
    • should work
  • Non-windows platform
    • NOT supported by engine
• Epplus engine
  • NOT supported by engine