improve performance of all websites dashboard when having thousands of websites

CHANGELOG.md

core/Archive.php

core/Archive/DataCollection.php

core/Archive/DataTableFactory.php

core/DataAccess/ArchiveSelector.php

core/DataTable.php

core/DataTable/Filter/ColumnCallbackAddMetadata.php

core/DataTable/Manager.php

core/Site.php

lang/en.json

plugins/MultiSites/.gitignore

plugins/MultiSites/API.php

...ltiSites/Columns/Metrics/EcommerceOnlyEvolutionMetric.php

plugins/MultiSites/Controller.php

plugins/MultiSites/Dashboard.php

plugins/MultiSites/MultiSites.php

.../MultiSites/angularjs/dashboard/dashboard-group.filter.js

...MultiSites/angularjs/dashboard/dashboard-model.service.js

...ns/MultiSites/angularjs/dashboard/dashboard.controller.js

...s/MultiSites/angularjs/dashboard/dashboard.directive.html