[Range aggregation] Allow min and max values to be computed from the data

[mastropi]

Goal: Show the actual minimum and maximum values of the X-axis variable in range aggregations, as opposed to having the user specify them.

Currently, the user needs to specify both the minimum and the maximum values of the X-axis variable, but most of the times they are not known in advance.

Notes about its implementation:

• The range for those bins should respectively show the minimum and maximum values observed in the data. Currently the minimum and maximum values are taken from the user input as they define the range aggregation bins.
• This change will also require a change in the backend.