axis configuration (log_scale, min/max extent)

This MR is the first enhancement for axis configuration.

By double clicking on column header, it's now possible to configure y min and max value, and also choose to plot data with logarithmic scale :

with linear scale

with log scale

It is also possible to do it in the column configuration dialog :

To save these informations, three parameters are created in the configuration :

• min (y min value)
• max (y max value)
• scale_type ("linear" or "log")

generate_config.py and the project has been updated with these parameters.