Data: Change getContent to return a Blob. Added getContentAsBuffer.
Interest: Change getNonce to return a Blob. Added getNonceAsBuffer.
Signature: Change getSignature to return a Blob. Added getSignatureAsBuffer.
KeyLocator: Change getKeyData to return a Blob. Added getKeyDataAsBuffer.
MetaInfo: Change getFinalBlockID to return a Name.Component. Added MetaInfo.prototype.getFinalBlockIDAsBuffer.
Name: Change getValue to return a Blob. Added getValueAsBuffer.
CHANGELOG: Deprecated the direct use of object fields. Changed Name.getValue(), etc. to return a Blob. Added deprecated getValueAsBuffer(), etc.