Extend ModifyTaskCmd for more data

[julianwr]

Scenario

• Library version: 1.4
• Description of your use case: (detailed description or executable reproducer, e.g. GitHub repo)
  I want to update data like followUpDate and dueDate of a task to implement features like postponement etc.

Current Behaviour

Not existing ModifyTaskCmd for updating followUpDate, dueDate etc.

Wanted Behaviour

Existing ModifyTaskCmd for updating followUpDate, dueDate etc.

Possible Workarounds