Debugging R_Add_Multibond by Naths script.
- 2 Ct ligands were wrongly named Cd
- redefined SJ (in older version Level 1 and Level 2 were identical)
Adding forbidden group to Intra_Diels_alder family

SOme of the rings with 3 conjugated double bonds undergo
intra diels alder to form highly strained rings. This
fix only solves one such case will possibly require hard coding
to eliminate all cases occuring under pyrolysis.