unu data: Print data segment of a nrrd file. The value of this is to pass the
data segment in isolation to a stand-alone decoder, in case this teem
compilation lacks an optional data encoding required for a given nrrd file.
Caveats: Will start copying characters from the datafile until EOF is hit, so
this won't work correctly if the datafile has extraneous content at the end.
Will skip lines (as per "line skip:" header field) if needed, but can only
skip bytes (as per "byte skip:") if the encoding is NOT a compression.
To make vol.raw contain the uncompressed data from vol.nrrd which uses "gz"
encoding: "unu data vol.nrrd | gunzip > vol.raw"
Usage: unu data <nin> [<out>]
<nin> = input nrrd (string)
[<out>] = output file (optional string); default: "-"
