- Updates hooks used to schedule welcome email

- Simplifies cron status message
- Implements newsletter change detection between scheduled queues
- Implements detection for subscribers who unsubscribed from list
- Implements detection for WP users who changed roles
- Updates scheduler worker logic
- Various fixes

assets/js/src/cron.jsx

@@ -63,13 +63,7 @@ define(
               {MailPoet.I18n.t('cronDaemonIsRunning')}
               <br/>
               <br/>
-              {MailPoet.I18n.t('cronDaemonWasStarted')}
-              <strong> {this.state.timeSinceStart} </strong> {MailPoet.I18n.t('cronDaemonLastExecuted')}
-              <strong> {this.state.timeSinceUpdate} </strong> {MailPoet.I18n.t('cronDaemonRunningDuration')}
-              <strong> {this.state.counter} </strong> {MailPoet.I18n.t('cronDaemonExecutedTimes')}
-              <br />
-              <br />
-              <a href="#" className="button-primary" onClick={this.controlCron.bind(null, 'stop')}>{MailPoet.I18n.t('stop')}</a>
+              <a href="#" className="button-primary" onClick={this.controlCron.bind(null, 'stop')}>Stop</a>
             </div>
           );
         break;