* Fixed ScatterChart to work like LineChart when are_values_columns is true
* Fixed labeling spaguetti and added offset.
* Fixed indentation to match GDScript style guide
* Fix distances calculations
Note that I removed the origin_at_zero conditional at calculate_coordinates because I already fix y_margin_min to 0 at structure_datas.
* Add missing features to ScatterChart
I added the missing features from LineChart to ScatterChart (like treshold and some properties) in preparation to creation of a Parent Class common to both. This way the changes can be traced easily.
* Add BaseClass for Scatter and Line Charts
* Changes to property_list getter
* Rename ScatterChartBase.gd to scatter_chart_base.gd
* Filenames changed to match GDscript Style Guide
From Godot so it doesn't break the links.
* Fixed some dependencies on chart and chart2D
