dragDataReceived
Asks the GtkTreeDragDest to insert a row before the path @dest, deriving the contents of the row from @value. If @dest is outside the tree so that inserting before it is impossible, false will be returned. Also, false may be returned if the new row is not created for some model-specific reason. Should robustly handle a @dest no longer found in the model!
Return
whether a new row was created before position @dest
Parameters
dest
row to drop in front of
value
data to drop