Import/Export mechanism

[rjzak]

Initially, an export system so some data may be exported and shared on malwaredb/data. But there should be a way to import data as well, and someday have MalwareDB instances share data between themselves.

For now:

• Export data: includes metadata, label(s), source information.
• Import data

There will be a reserved username for imports, and probably be reserved names (or UIDs) for service accounts.