Denote all available fields for `wp comment list`
Denote available fields for `wp cron schedule list`
Denote available fields for `wp menu list`
Denote relevant available fields for `wp menu item list`
Fix display of menu item classes in list table
Denote available fields for `wp menu location list`
Denote available fields for `wp plugin list`
Denote available fields for `wp theme list`
Formatting
Denote available fields for `wp post list`
Denote available fields for `wp role list`
Denote available fields for `wp sidebar list`
Denote available fields for `wp site list
Denote available fields for `wp term list`
Denote available fields for `wp user list`
Denote available fields for `wp widget list`
Ensure all non-section header bodies are indented
Merge pull request #1352 from wp-cli/list-fields-1352

Add "Available Fields" to docs for list commands