[BUG] Allow the Y axis to manage and display non-integer numbers

[MLAuger]

With the chart plugin in RAMP, we can manage the decimal numbers display on the Y-axis range slider.

Currently with GeoChart, it seems the Y-Axis slider can only use integer numbers. This is very limiting.

Example in RAMP:

Same dataset in Geoview with Chart:

In this example, the Y-axis slider can't move on any intermediate position between 0 and 1. The slider forces the handles on either of those value which returns empty charts for both positions: 0 or 1, since none of the table entries has any of these two value.