Config param for ETL time-window for BigQuery sources

[gmcfall]

I want the ability to specify the time-window for records that will be injected into an ETL pipeline.

Acceptance Criteria

• There must be a batchBegin configuration property which specifies the beginning of the time window.
• The modifiedDate property shall be used as the end of the time window.
• With the exception of the target shape, the pipeline shall exclude records that are outside the time window.
• When the target shape is also a source shape, the pipeline shall exclude records that are later than the modifiedDate property.