no_regioisomer filter could be useful

[KramerChristian]

Double- and triple-cuts can produce regioisomers, where the constant parts are just swapped. Examples are these transformations:

Double cut: [:1]CC1(CC1)[:2] >> [:1]C1(CC1)C[:2]
Triple cut: [:1]c1cc([:2])c([:3])cc1 >> [:1]c1cc([:3])c([:2])cc1

It may be useful to not store these transformations in order to reduce database size, in particular for triple cuts. If implemented, it would be good if these filter can be set separately for double and triple cuts.