Move request_graph.py to server side

[Ezibenroc]

The execution of request_graph.py implies to send a lot of data for nothing.
We could reduce this by moving the script to the server, and sending only the useful data.

For instance, if the user wants some stats with a granulometry of 1h, send:

[['2015-03-01 09:00:00', 3]]

instead of:

[['birth date of "charles maurras"', '2015-03-01 09:59:03.390558'],
 ['birth date of charles maurras', '2015-03-01 09:58:49.990248'],
 ['birth date of maurras', '2015-03-01 09:58:42.594906']]

Moreover, the number of data to send will be reduced since we will send only the data for the relevant interval, not all the queries.

The parameters to add to the API would be a parameter to choose what data the user wants (the queries or only the stats) and the parameters interval and granulometry.

Then, in request_graph.py there will only remains the code to generate the graph.