This commit introduces a new output stream, 'RFT', that is intended
as a new backend for writing RFT files. At present this supports
integer, float, and PaddedOutputString<8> element types since those
are the types needed for basic RFT data. We will extend the element
support if needed for PLT and/or Segment data.
We support formatted and unformatted output streams and distinguish
between opening a new stream and opening an existing output stream
(essentially between open modes ios_base::out and ios_base::app).
Add unit tests to exercise the possible combinations.
a281a3c6f4