Add quote parameter to accepted_values test

[clausherther]

Describe the feature

Currently only character values can be tested in the built-in accepted_values test.

Relevant code from accepted_values.sql

select
        value_field

    from all_values
    where value_field not in (
        {% for value in values -%}

            '{{ value }}' {% if not loop.last -%} , {%- endif %}

        {%- endfor %}
    )

To support testing both accepted numeric and character values, we should make quoting the values optional.

Additional context

https://getdbt.slack.com/archives/C2JRRQDTL/p1572299083481900
Per a Slack conversations with Claire and Drew, this should not break existing uses of this test.
Drew suggested added a quote parameter, the default of which should be true, which is the current behavior.

Proposed change

{% set quote_values = kwargs.get('quote', True) %}

    select
        value_field

    from all_values
    where value_field not in (
        {% for value in values -%}
            {% if quote_values == True -%}
            '{{ value }}'
            {%- else -%}
            {{ value }}
            {%- endif -%}
            {%- if not loop.last -%},{%- endif %}
        {%- endfor %}
    )

Who will this benefit?

All users that use the accepted_values test.

[clrcrl]

You can change {% if quote_values == True -%} to be {% if quote_values -%}

[clausherther]

Wasn't sure how that worked in Jinja, thx!