Upgrade docs site to support 0.16.0 functionality

[drewbanin]

Git is hard! Reopening from #2178

resolves #1671 in dbt-core, plus other issues via https://github.com/fishtown-analytics/dbt-docs repo.

Changes via:
dbt-labs/dbt-docs#69
dbt-labs/dbt-docs#70
dbt-labs/dbt-docs#71
dbt-labs/dbt-docs#72
dbt-labs/dbt-docs#73
dbt-labs/dbt-docs#74
dbt-labs/dbt-docs#77

Description

• Handle non-array accepted_values test arguments (dbt-docs#70)
• Support filtering by resource type (dbt-docs#77)
• Render analyses, macros, and custom data tests (dbt-docs#72, dbt-docs#77, dbt-docs#69)
• Support hiding models from the docs (these nodes still render in the DAG view as "hidden") (dbt-docs#71)
• Render meta fields as "details" in node views (dbt-docs#73)
• Default to lower-casing Snowflake columns specified in all-caps (dbt-docs#74)
• Upgrade site dependencies

Checklist

• I have signed the CLA
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• I have updated the CHANGELOG.md and added information about my change to the "dbt next" section.

[drewbanin]

@beckjake FYI I'm going to merge this!

Examples of changes:

• meta fields for models
• hidden models
• document macros
• document custom data tests
• adapter macros
• document analyses

[beckjake]

Sounds wonderful - I'll sync up dev/octavius-catto once you do!