Neuronexus 4 shank 2 tetrode silicon probe map

added functions to network module to retrieve acquisition/recording status and the current recording path

- Sync signal, wired to BNC out with the update rhd2000.bit, can be set
  to a multiple of the sample clk period using the RHD2000Editor
- This commit corresponds to this pull request:
  https://github.com/open-ephys/rhythm/pull/11

Fixed bug in NetworkEvents::createZmqContext.  Added Python example script for sending network events.

Included unistd.h for successful Linux compile, known fix from https://github.com/open-ephys/GUI/pull/150

0MQ is included, but not linked (unless you define it in
NetworkEvents.h).
Redrawing events are not called for some reason.