Add partitioning_column

[lucadelu]

Hi,
I'm new to TimescaleDb and I'm starting to use it in a Django project.

I'm interested to use django-timescaledb, I would like to use the partitioning_column option of the create_hypertable function but it seems not supported yet, right?

I could be interested to make a pull request to add this support.
I was thinking to implement it with these changes:

• add a new set of models fields (like TimescalePartinioningCharField, TimescalePartinioningIntegerField, TimescalePartinioningForeignKeyField)
• modify _create_hypertable functions (postgis / postgresql ) and related functions calling it to support this new models fields