MetriDyne sites: fleet control panel

Changes made here apply to every site in the multisite install.

Configuration (System, Site, Plugins, Themes) saves to the shared settings in user/config. Every site inherits them, except values a site sets in its own user/sites/<host>/config.
Updates (Grav, plugins, the metritheme theme) are installed once and used by all sites.
Each site's own admin (for example central.metridyne.com/admin) is for that site's pages, images and accounts.

Created and maintained by StoneFly Technology, Saint George, Utah.