Mailmotor: added changelog
Mailmotor: added settings_campaign_monitor

@todo: later we will automatically generate a settings page per mail
engine.
Mailmotor: settings page updated
Mailmotor: config.php: mailmotor added
Mailmotor: integrated functions in model
Mailmotor: helper files for Mailchimp and CampaignMonitor
Mailmotor: locale: MailEngine added
Mailmotor: settings template added