Add CLI option to exclude specific schema/custom tests

[jmak123]

Please make sure to fill out either the issue template or the feature template and delete the other one!

Feature

Add CLI option to exclude specific schema/custom tests

Feature description

Currently dbt does not allow using tags with tests. Suggest adding functionality to tag tests like model to allow using exclude in dbt test.
Also recommend modifying existing dbt compile output behaviour to generate names (and scripts) of tests in folder target so users can access those names and use exclude on them more easily.

Who will this benefit?

Some tests take significant time to complete and adding tags functionality would give users more flexibility with test scheduling.

[drewbanin]

Thanks for making this issue @jmak123! Check out this semi-related discussion: https://discourse.getdbt.com/t/pre-proposal-column-tags/433/4

[beckjake]

Fixed in #2039 - added tags on columns (which push down to all tests for a given column) and tests themselves.