Add isRowExpandable prop for DataGrid component for better user experience

[gradolol]

I often have cases when I need to display information about a row with expand, but when I open it, I see empty data.
For example, a list of events with children and parents. For a child event, I don't want to show "expand" because I know that this row doesn't have any data.

My solution is implement prop like isRowSelectable.

[fzaninotto]

Fixed by #5941