Add python examples for offboard control and sensor combined listener

[haotianh9]

In respond to this issue in PX4-user. I wrote python examples for offboard control and sensor combined listener and put them in the scripts folder. I have tested they behave the same as the original cpp version .

[haotianh9]

Maybe there is a mistake, when I begin to write the python version, I added some comments in the original cpp file to help me in developing, but I made a mistake to commit and push this change. Thus at the end, I downloaded the original file and replaced my version. Seems this caused some problem. I'd like to ask if you can help me with this issue.

[hamishwillee]

@TSC21 Is this something you can help with?