draft implementation of hard_factorized (not working yet)
partial fixes of the new factorization - not finished yet
partial fixes of the new factorization - working but should not be optimal yet
cleanup a bit factorized sums (plus/minus simplification) to spare a few code lines
fix + do not overexpand expressions
deactivated hard_factorized because it actually slowed down
first implementation of soft factorization
move out spurious negative sign after soft sum factorization
tested soft factorization - did not bring much
INSERT_EARLY - gained about a second on DFT1024 tests
looser precision + deactivated soft factorization -> better results, esp. for cooley-tukey