Only show dataframe contents once

[thesimonho]

Currently you can click on a dataframe to show its contents in a separate window, but if you click the dataframe name again in the inspector it will open another window with the same contents, leaving you with 2 (or more) identical windows

Would it be possible to first check whether the dataframe is open, and if it is then set focus to the currently opened window instead of opening a new one?

[lckr]

Thanks @sho-87, I will look into it.

[NoRaincheck]

Just realised this one is related to #69