This allows mattermost to use a non-tls connection with a SMTP server that
supports PLAIN auth (but not LOGIN). The go library explicitly allows PLAIN
auth over non-tls connections - https://golang.org/src/net/smtp/auth.go#L55Fixes#2929
* PLT-3647 Added config settings for email batching
* PLT-3647 Refactored generation of email notification
* PLT-3647 Added serverside code for email batching
* PLT-3647 Updated settings UI to enable email batching
* PLT-3647 Removed debug code
* PLT-3647 Fixed 0-padding of minutes in batched notification
* PLT-3647 Updated clientside UI for when email batching is disabled
* Go fmt
* PLT-3647 Changed email batching to be disabled by default
* Updated batched email message
* Added email batching toggle to system console
* Changed Email Notifications > Immediate setting to a 30 second batch interval
* Go fmt
* Fixed link to Mattermost icon in batched email notification
* Updated users to use 30 second email batching by default
* Fully disabled email batching when clustering is enabled
* Fixed email batching setting in the system console
* Fixed casing of 'Send Email notifications' -> 'Send email notifications'
* Updating UI Improvements for email batching (#3736)
* Updated text for notification settings and SiteURL.
* Prevented enabling email batching when SiteURL isn't set in the system console
* Re-added a couple debug messages
* Added warning text when clustering is enabled
* Reorganized system console
* Fixed the names of some components
* Fixed timestamp for BrandImageSetting
* Fixed merge issues
* Updated push notification settings to match master branch
* Removed top level setting pages and moved enable Gitlab/LDAP settings onto their respective pages
* Re-added restrictDirectMessage setting to system console
* Re-added email connection test and fixed some margins
* Fixed ESLint errors
* Renamed Authentication > Onboarding to Authentication > Email in the system console
* Renamed Customization > Whitelabeling to Customization > Custom Branding in System Console
* Re-added EnableOpenServer to system console
