GPL version of Javascript Gantt Chart
https://docs.dhtmlx.com/gantt/whatsnew.html#806
https://docs.dhtmlx.com/gantt/whatsnew.html#805
https://docs.dhtmlx.com/gantt/whatsnew.html#804
https://docs.dhtmlx.com/gantt/whatsnew.html#803
https://docs.dhtmlx.com/gantt/whatsnew.html#802
https://docs.dhtmlx.com/gantt/whatsnew.html#801
https://docs.dhtmlx.com/gantt/whatsnew.html#x6560x80x6561x
https://docs.dhtmlx.com/gantt/whatsnew.html#7113
https://docs.dhtmlx.com/gantt/whatsnew.html#7112
https://docs.dhtmlx.com/gantt/whatsnew.html#7111