[Python] Allow configuration options to be set when creating BallistaContext

[andygrove]

Is your feature request related to a problem or challenge? Please describe what you are trying to do. The Python bindings for BallistaContext have hard-coded configuration settings that cannot be overridden, so it is not possible to tune jobs.

Describe the solution you'd like Allow configuration options to be set when creating BallistaContext

Describe alternatives you've considered None

Additional context None