Added a verbose warning when trying to sniff on a global scope
on ROS - that is not implemented (needs 3rd party stuff (?)).
You need to specify a list of categories for now when using ROS.

Docs addendum: you can specify - as out/input file to use stdout/stdin

Can be used to record IU event streams to session files, and replay
these session files. The recorder looks mostly like the sniffer, but
also writes to a file. Replay timing is taken from the file, relative
to the first considered event. Automatic retraction is suppressed in
the replay script (only replicating original retractions).

Current limitations:
  - only ADDED, UPDATED, RETRACTED, MESSAGE, COMMITTED (-> TODO links!)
  - (replay script:) uses list of categories, no regex mode so far

Example usage:
 ipaaca-session-record --rsb-host host1 -r -c "asr.*" -o my.session
  [...]  # partial local replay:
 ipaaca-session-replay -c asrresults asrstate -i my.session

Start ipaaca-pong on one system to listen for and reply to ping IUs.
ipaaca-ping on the other hand will send these pings and report round
trip times and estimated system clock difference.

Arguments:
  --delimiter delim             field delimiter, default '\t'
  --strip                       call strip() in each field first
  --fields name1 [name2 [...]]  fields to print (in order)
                                defaults to: 'time' 'text'

* Filtering by IU event type.
* Description of sniffer arguments after startup now prettier.

Manually integrated the following changes from b8466a (master 2015-11-13)

- Blackboard classes by hvanwelbergen
- Blackboard test by hvanwelbergen
- Payload merge fix by hvanwelbergen
- rsb Buffer fix (by myself) copied but inactive (not needed atm?)

Please refer to the logs of the legacy-str branch for a full history
of the respective changes.

Sniffer: only display quotes for string-type payload values
Injector: using unicode() and catching errors

ipaaca-iu-sniffer optionally takes a list of category arguments
(if not specified, it still listens for everything).
ipaaca-iu-injector needs to be provided with a category name
and, optionally, with key-value pairs for the payload, as such:
$ ipaaca-iu-injector  murmlfile  data  smile_3sec.us