Raise ValidationError if attribute type is missing

Change-Id: I92c88f6ee50183a6f2c36cf370dd4b15e56a227c
Closes-Bug: #1386717
Record and retrieve table creation timestamp

Extend the magnetodb.table_info table with an additional
"creation_date_time" column to store the creation timestamp of each table.
Return the creation timestamp in relevant REST API calls.

For consistency, renamed the last_updated column to last_update_time_date.

Closes-Bug: #1298814

Change-Id: I02b920b866529027655802c4d880f7557329824a
Merge "Record and retrieve table creation timestamp"
Fix table schema synchronization

Closes-bug: #1388920

Change-Id: I7db1424ac0fc8c2853b829ff90041459599fbe7e