* fix(graph2d): fix#2500 for graph2d; improves #2580
* fix(DataSet): make sure the right id-type is used internaly
This fixes a fixed strange string-number conversion issue.
It can happen that id "0" !== 0 what causes #2580.
fixes#2580
* generate individual css files; fixes#1969
* simplified css bundleing
* add new generated dist-css files
* use chart specific css files in the examples