Add multiprocessing for generating dashboards to reduce provisioning time

when processing data from the inventory_provider poller/interfaces endpoint BDM now uses dashboards_info rather than dashboard_info
dashboards_info contains a list of objects rather than dashboard_info which contains a single object

potentially other fields too, although it's not immediately clear if this would be useful

Most fields need the conversion, so make it explicit when not required

This reverts commit cd8d7f3b.

Put EUMETSAT under services on home dashboard.

Dashboard generation now depends on dashboards obtained from Inventory Provider.