When period=range, exporting data below an evolution graph should export data per day

[mattab]

When period = range, the evolution graph show daily data.

When exporting the data below a graph (eg. in XML or JSON) then the result set should also contain "daily data". Currently it shows the sum of all data.

[mattab]

In db6199d: When period=range, exporting data below an evolution graph should export data per day Fixes #4777 and PR #233