handle `DataTable` with no attribute and `otherEntity` with Attribute level metadata

[brunj7]

We have now these two new cases, where:

• DataTable is not required to have attribute level metadata (see Accept EDI and LTER data package inputs #106 for more)
• OtherEntity can have attribute level metadata (see Check compatibility with metadata created by online form #105); actually, this is the new norm for data packages made using the webform