MAINT: SEPP-refs production-mode (qiime2#438)

Revert "MAINT: drop BIOM v1.0.0 (qiime2#427)"

This reverts commit 3e0bf80.

MAINT: Moving pictures updates (qiime2#404)

- DADA2 1.10
- Misc grammar

MAINT: New feature classifiers, 2019.1 (qiime2#385)

BUG: Remove missing doc page comments (qiime2#367)

MAINT: Update install guide; New copyright year (qiime2#284)

Fixes qiime2#279
Fixes qiime2#283

MAINT: include q2-cutadapt in list of plugins (qiime2#261)

BUG: filename re-used in longitudinal tutorial (qiime2#251)

MAINT: update beta-correlation to mantel (qiime2#218)

ENH: plugin directory supports multiple interfaces (qiime2#206)

The plugin directory now displays CLI and Artifact API help text for actions instead of a custom table of inputs, parameters, and outputs (this table was generally confusing to users).

Thanks @thermokarst for having the idea of using the help text that's already being generated for the CLI and Artifact API! The code is much simpler now too :)

Also, instead of using an action's underscored name (`Action.id`), the action's CLI name (dashed) is used in URLs and content.