Establish a mime-type and file extension with IANA

[elliottinvent]

Once we have submitted CompactData as an Internet Draft (#1) then we should agree on a mime-type and file extension so we can submit to the IANA standards tree.

For example:

• MIME-type: application/compactdata
• File extension: .compactdata

compactdata is too long, so we'll agree on something else in a non-public forum and prepare the filing to be sent to IANA once the Internet Draft is ready.