Feature: Add Sequence Settings options for sending alerts to members when new content is available.
 Added basic cron support for new content check
 Added member page links for new content
 Added new settings/options for sequence meta data.
 Added support to settings for selecting template to use for new drip content alert (per sequence).

 TODO: Missing back-end support for alert template (using the selected template). Missing back-end support for admin defined schedule for new content cron job. Want to add "Publish" metabox behavior for drop-down & edit of drop-downs.