Merge remote-tracking branch 'fariba/master' to fix Intra_R_Add_Endocyclic

This hopefully fixes all the remaining bugs in Intra_R_Add_Endocyclic
that were due to Cdd atom types being excluded from the list of
carbons with double bonds (Remember Cd means C with only one double bond.)

We also added some comments to the longDesc fields to help explain the tree.