Add charts base tests

Add base tests for all Chart classes (except BoxPlot),  and DataAdapter.

Test are not enough to say Charts are well covered by test but are a good foundation and test classes can be used from now on to add more tests, refactoring and to be extended when adding specific features
Good spot! Must remove it.
I used it in a few iterations to understand why the segment was overlapping with the circle glyph.. The issue was happening because I was drawing the circle glyph before the segment.