Take full advantage of asynchronous request execution

[MariusWirtz]

There is currently no way to take full advantage of asynchronous request execution (asnyc_requests_mode).

It would be nice if TM1py could return the job-id to the calling function. This way python scripts could easily do stuff in parallel while polling the operations in TM1 to see if they are finished yet.

Reference: https://gist.github.com/rclapp/2d6d8d389b99838d6e0fec18642e658f