Lucid Meetings Support Portal

Fixes:

* Close the preview modal when rendering a different agenda item
* Agenda organizer -- recover when moving an agenda item doesn't result in a notification
* Corrections to add-attendee-from-email

Improvements:

 * Google calendar integration

 * System and error logging improvements

 * Meeting export cleanup and error handling

 * Sign in and sign up pages

 * Cleanup for deprecated integrations (Box viewer replaced crocodoc)

 * API update: expand the definition of managed accounts.
 * Add cover images for template guides

 * Minor tweak on template about section

 * Add a user pref for page size for paginated listings.

 * Improve the attendance table for more consistency with other tables.
 * Improve pagination consistency for admin pages
 * Improve the Explore & Learn menu
 * Improve the ability to support invoice billing
 * Improve the Site Manager area

 * Show the billing type on the annual passes admin page.
 * Tweak the site manager page to move a couple links to the top.
 * Improved Zapier integration support.
 * Encourage people to contact support for invoice billing.

New features:

* Update to latest box previewer; add support for single-page presentations and add svg and csv to the previewable list

* Create a page-o-guides and an Explore menu.

* Add an external link to the glossary to the Explore menu.