DbDump to print datatype if exists in revMeta

Also, snappy_uncompress document if document's
datatype indicates that document is compressed, as
content_meta will not carry COUCH_DOC_IS_COMPRESSED
flag.

Change-Id: I90e824e29bd2fb89e65a1370f45f4b4b00570360
Reviewed-on: http://review.couchbase.org/41426
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Sundararaman Sridharan <sundar@couchbase.com>