Copy pasting cells with formulae between files does not store the formula in the new file

#### Description:

If one copy pastes cells with BHoMFormula to a sheet without the same BHoM formula in it, for example to a new sheet, it runs fine whilst still open. Saving the new sheet and closing it though, the formula does not load up, but gives a `#NAME` value in the cell. Adding the formula used to another cell of the sheet, the cell starts working again.

Seems as copy pasted cells containing BHoM calls do not get correctly serialised to the sheet.

#### Steps to reproduce:

- Open a fresh sheet
- Add some BHoM method call
- Open another new sheet
- Copy paste the cells containing BHoM calls to the new sheet
- Save and close the sheet containing the pasted cells
- Re-open the saved and closed sheet

#### Expected behaviour:

For copy pasted BHoM formulations to be saved

#### Test file(s):

No needed/possible