Python: add Payload and TransactionOptions

[Thoralf-M]

Description of change

Please write a summary of your changes and why you made them.

Links to any relevant issues

#129

Type of change

• Breaking change (fix or feature that would cause existing functionality to not work as expected)

How the change has been tested

Running the new example

Change checklist

• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have checked that new and existing unit tests pass locally with my changes