Fix execute variable in macros & enable get columns in adapter

Previously the variable execute when read inside macro's would always be false - as when the macro was compiled it was false, and the macro's compilation context was still present. This change passes in what ever the current execute variable value is.

This commit also adds the ability to get the columns in a model using the adapter method adapter.get_columns_in_relation

Upgrade golang to support M1

Upgraded the Go language version to 1.16 to support apple silicon.

Flag for Enable Schema Tests

This version adds a flag to turn on/off schema tests enable-schema-based-tests
This can be used by calling -s=true or --enable-schema-based-tests to enable ddbt to run schema tests (the ones in your yml file)

BigQuery logical view support

This version adds support for views in BigQuery to ddbt.
This can be used as a materialization='view' model config, and ddbt will create (and replace) the models as views instead of tables.

Add `test-gen` command and doc suggestions in `schema-gen`

• New command added test-gen which automatically scans the models given and suggests tests to be added to the model schema. At current version only allows for unique and non_null test.
• schema-gen now has doc string suggestions for models by searching the dbt project docs directory.

Add lookml view generation command

This release adds ddbt lookml-gen command which automatically produces a .lookml.view file based on model in user's dev branch. This saves tedious .lookml.view text editing when adding new model to Looker.

Isolate DAG and schema-gen bugfix release

This release includes the following bugfixes

• Multi model selectors for ddbt run where you can specify multiple -m model flags #25
• Generate stub config block for upstream models for isolate-dag command #26
• Support materialization macros for isolate-dag command #27
• Adds a -m model parameter for the schema-gen command #28

We're skipping a few minor releases because DDBT developers work too fast! 🏎️

Bug fixes

Increment the version of DDBT and include bug fixes from v0.4.1

add `ddbt schema-gen` command to DDBT

The monzo dbt repo has a useful custom command dbt monzo schema-gen which automatically produces a yml schema file based on changes made to a model on someones dev branch, saving tedious yml text editing.

This version of ddbt will have similar functionality that runs in a fraction of the time. The command ddbt schema-gen model will produce a new yml file for new models, and an updated yml file for existing updated models.

Addition of `isolate-dag` command

This release adds the isolate-dag command which can be used to create a shadow of large DBT projects isolated to just the elements you need for the DAG run.

This isolated version of your project can then be used with Fishtown's DBT, allowing you to benefit from the speed increases of DDBT but the compability of DBT (incase your project uses something that DDBT doesn't support yet)