Adds two new features to collect and show useful analytics.
Usage Statistics:
* Begin tracking daily active users who log in and interact with major features
of the website each day, such as the chat room, forum and gallery.
Demographics page:
* For marketing, the home page now shows live statistics about the breakdown of
content (explicit vs. non-explicit) on the site, and the /insights page gives
a lot more data in detail.
* Show the percent split in photo gallery content and how many users opt-in or
share explicit content on the site.
* Show high-level demographics of the members (by age range, gender, orientation)
Misc cleanup:
* Rearrange model list in data export to match the auto-create statements.
* In data exports, include the forum_memberships, push_notifications and
usage_statistics tables.
* Add support for Web Push Notifications when users receive a new Message or
Friend Request on the main website.
* Users opt in or out of this on their Notification Settings. They can also
individually opt out of Message and Friend Request push notifications.
