Get AIP running on multiple datasets

[MattWellie]

Issue: Closes #489

• AIP implementation here ran on the default dataset config[workflow][dataset]
• When running on multiple cohorts, the dataset is always seqr
• Alter scripts to take a dataset argument, which is used to read the specific parts of config.
• Additional: Config was being sourced before AIP-specific default content was loaded, so the early get_config needed to be cut out