parse FileRecord.

changed Attribute parsing style.
refactored AttributeMap into its own class.
swooooooosh!

Have Attributes return their payload as InputStream instead of ByteArray.
Return InputStream provider, since a Stream is consumed once read.
impl AbsoluteDataStream.

Allows absolute access to an InputStream by closing and re-opening the Stream via a StreamProvider.
split between Attribute header and payload.