Scatter charts should be on all data, not current page only

[alexgarel]

Problem

#189 introduced scatter plot, but they are only based on current page results, while we would like to see results from whole dataset

Proposed solution

In build_charts, gather data we need to get, and relaunch a search with same query but getting only needed data to draw the chart.

Based on the count from the search (as we already launched search):

• either add a hard cut on the number of results (should be configurable, defaults to 1000)
• either remove the sort option (little optimization) when we are under the hard cut