Check date/time types

[mccalluc]

John reports that they aren't coming through as dates... If there's older data, that can't be fixed, except at index time, but perhaps we can be more strict going forward.

Date fields are not mapped in elasticsearch as dates. The strings for date fields are in inconsistent formats and cannot be sorted as is. All date fields except for last_modified_timestamp have been removed.
end_datetime: datetime
execution_datetime: datetime
procedure_date: date
start_datetime: datetime
library_creation_date: string. Is a string?