ctf: Fix API inconsistencies

ctf: Fix API inconsistencies

Some API methods would return or take as parameter classes
that were not part of the API themselves. This little rework
seems to fix the problem, mainly by exporting BitBuffer, Stream
and StreamInput.

Change-Id: I3bac3619426d51c1a1484a6a0a336ec93e700175
Signed-off-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Reviewed-on: https://git.eclipse.org/r/9173
IP-Clean: Matthew Khouzam <matthew.khouzam@ericsson.com>
Tested-by: Hudson CI
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-by: Bernd Hufmann <bhufmann@gmail.com>
IP-Clean: Bernd Hufmann <bhufmann@gmail.com>
Tested-by: Bernd Hufmann <bhufmann@gmail.com>