Changed Collector interface to indicate support creation of produce- and
consume commands whereby supporting better command composition for
clients, i.e. for embedding of such commands.

Replaced usage of
SnapshottingTranscriber.Connection.LocationCommandsPair with usage of
ReversibleCommand in transcriber.
Added support for creation of produce- and consume commands in
transcriber.

Signed-off-by: Jakob Brandsborg Ehmsen <jakobehmsen.github@gmail.com>