add zoom to scatterplot

[Kvaz1r]

For #84 .

There isn't anything really new - all changes just copy-pasted code from wxmath2dplot.

[Anton-V-K]

Any plans to merge these changes? :)

[helha54]

I tried the code-changes (from thefile-changes) but it failed with shredptr.h(85): assert "m_ref!=_null" failed in operator ->0

I try to minimize the xy-dots to smaller points from the size like ball's (as it is now)

[Kvaz1r]

I tried the code-changes (from thefile-changes) but it failed with shredptr.h(85): assert "m_ref!=_null" failed in operator ->0

I try to minimize the xy-dots to smaller points from the size like ball's (as it is now)

1. Code in this PR doesn't contains anything that can lead to break not null assert. I think that reason the same as in StackedColumnChart can't take more than 3 datasets #165. 3 datasets is current restriction for all charts.

2. As for now radius for scatter always equals 5, but you can change the value here and re-build the library.

[helha54]

I found the reason. There are two lines missing in, when re-insert them everything is ok. That is one include-line
#include "wxchartstheme.h"

wxScatterPlot::wxScatterPlot(const wxScatterPlotData &data,
const wxSize &size)
:m_options(wxChartsDefaultTheme->GetScatterPlotOptions()),

where the last line ' : m_opions' is missing

After inserting them everything is ok.

[helha54]

I reduced the point-size to 1 and that is what i needed.

I run scatterplot with 5 datasets, so it seems to work with 5 datasets least. ( just as information)