Prevent extract formula refactoring on formulas with relative references

[dhoepelman]

Currently the EF refactoring behaves incorrectly when the subformula contains relative references and the target is a single cell.

E.g. =A1+1 and =A2+1, extract A1 to $B$1. B1 will then contain =A1, and both previous cells will contain =$B1$1+1