ATLAS: descriptive text for external resources

* Adds descriptive text to `atlas-external-resources.xml`.
  (closes #487) (PR #523)
ATLAS: derived dataset descriptions

* Amends descriptions in `atlas-derived-datasets.xml`.
  (closes #485) (PR #524)
UI: new updated homepage proposal
search: facet fix

* fixes javascript errors for facets
Populate temp data for glossary