Change the global String Template group structure to welcome highchart in the familiy
Common : html, data, chartbody
LibrarySpecific : imports, charts, graphs
Separating string templates in folders :
	- common
	- 1 per library
In code generation, use of several STgroups
Design of the String template representation of highchart
First highchart visualization : Pie chart
Fix the HighChart data format transformation (it's not JSON, bouh)