reformat Bonsai network response

[vga101]

Hi Bernd,
I've changed the Bonsai network response format to reflect our current expectations: responses should always have the same format, just reflect the type of original request in their "response" field. Check whether you feel happy about the implementation. :-)

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Update network json response updated to new specification:
for any requests, responses should be formatted as
{"user_particles": [0, 0, 0, 0], "simulation_time": 89.4, "response": "release"}
{"user_particles": [0, 0, 0, 0], "simulation_time": 89.4, "response": "remove"}
{"user_particles": [0, 0, 0, 0], "simulation_time": 89.4, "response": "report"}
The "response" field reflects the request name that triggered the response.

[BerndDoser]

Looks good, especially the user_particles as array is much better. Instead of the hard coded 4 we can use WOGManager::number_of_users. I change it after the merge.