Script Generator: Pasting a row into a cell

As a user I would not like unexpected behaviour when pasting rows into the script generator. Following https://github.com/ISISComputingGroup/IBEX/issues/5965 it is now possible to copy and paste rows much more nicely. However, the following leads to unexpected behaviour:
* I copy a row
* I select a specific cell (not a row)
* I paste
* The cell is now filled with tab separated values from the row I copied

## Acceptance Criteria
* A more intuitive behaviour is agreed upon
* In a meeting on 28/01/21 with @DominicOram, @Tom-Willemsen, @RaiBishal and @John-Holt-Tessella we agreed that the more expected behaviour would be that if you are pasting tab separated data into a row's cell it should still just create a new row
* The solution is implemented