Use 'cql.allIndexes=1` when no query is supplied, instead of a wildcard

At present, if you turn on a filter in the Users app when there is no query string, a "find all records" query-string of username=* is used. This is inelegant and potentially inefficient. Instead, the special CQL query cql.allRecords=1 should be used, as it is in the Inventory and Codex Search apps.