Add option for hierarchical tabs

[MaximilianZenz]

I think it would be great for usability if tabs that gets opened by other tabs will have the tab where that it got opened from as a parent tab so that you automatically get a hierarchical structure. for example if you search something on google all the tabs you open from that google search should be hierarchical below that google tab. with that functionality it would be possible to trace from which tabs you came and its easier to go back.