Eliminate WP_CLI short-circuit

Stream needs to be more thoughtful with regards to how it behaves when WP-CLI is activated. With this short-circuit in place, plugin activation was prevented via WP-CLI:

> PHP Fatal error:  Class 'WP_Stream_Admin' not found in /srv/www/wordpress-develop/src/wp-content/plugins/stream/includes/install.php on line 83
Use WP_CLI::warning() for admin notices in WP_Stream
Allow for author=0 (WP-CLI) to be queried
Attribute anonymous WP-CLI actions, and tag WP-CLI actions done by a user
Include WP-CLI (user=0) in filter selects
Merge branch 'develop' into wp-cli

Conflicts:
	stream.php
Delete new DB version after uninstall
Only show uninstall message when a database_message is supplied
Refactor for WPCS master rules
Fix another assignment alignment problem
Fix inclusion of placeholder for authors filter when WP-CLI included
Apply style issues reported by review
Fix Ajaxified filters in Stream list table
Short-circuit author list generation if users are more than PRELOAD_AUTHORS_MAX
Fix pre-selection of ajaxified filters
Remove WP-CLI user if there are no records attributed to user=0
Unslash search query param
Generalize the ajax-filter pre-selection code
Remove dummy ajax callback method
Show proper author gravatars on ajaxified filters
Include WP-CLI user in list returned on Settings page