I just quickly went through patch v5.
It's rather big patch, on (or beyond) my knowledge of PostgreSQL to perform high-quality review. But during this week I'll try to send reviews of parts of the code, as going through it in one sitting seems impossible.
One proposed change - update copyright to 2016.
i'd also propose to change of pglogical_output_control.in:
comment = 'general purpose logical decoding plugin'
to something like "general-purpoer plugin decoding and generating stream of logical changes"
We might also think about changing name of plugin to something resembling "logical_streaming_decoder" or even "logical_streamer"