Update logic of smart_source macro to consider DBT_POPULATE_DEV_TABLES environment variable if it exists

Updated the logic in smart_source macro to populate the tables in the development environment in standard datasets. Add an environment variable DBT_POPULATE_DEV_TABLES and set it to TRUE if the environment variable does not exist it will continue with the default behavior. The DBT_POPULATE_DEV_TABLES is not mandatory it is only required if you want to populate your development environment with actual data using the smart_source macro. The macro assumes the default value of DBT_POPULATE_DEV_TABLES as FALSE if it does not exist

Add columns to the save_test_results macro

Add columns to the save_test_results macro.
Details on macro behavior and usage are available in the README.md.

Not null constraint

Adding not null constraint package to the dbt utils package
Please refer the README.md on the usage of this macros

Add macro to save results of dbt tests to a BigQuery table

Add macro to save results of dbt tests to a BigQuery table.
Details on macro behavior and usage are available in the README.md.

Adding materialized views to the gmi common dbt utils package

Adding materialized views package to the dbt utils package
Please refer the README.md on the usage of this macros

General Mills dbt package first release

First release of gmi common dbt utils package
Please refer the README.md on the usage of these macros