ENH: Add ability to create datasets using the gbq module
Removed the `bq` command line module from `test_gbq.py`, as it doesn't support python 3. In order to do this, I had to create functions for `create_dataset()`, `delete_dataset()` and `dataset_exists()`.

This change is required for #11110

At the same time, I also implemented the following list functions: `list_dataset()` and `list_table()`.
