intra_substitutionS_isomerization accessibility

rearrangement of entries to meet accessibility tests
-Remove an R atom on all backbones which should be part of an end groups
-Also remove same unlabeled R atom on most general end group S-RR as it is not a reacting group and not necessary. This maintains the requirement that the subgraph of backbones must be the same as the most general end node.
-*3 subtree was overspecified for many groups. I have removed many of these groups and reduced the rest. This applies to all groups below CdsJ in that subtree.
-Changed names in rules accordingly
-To accommodate rule number 3, I have created a new group which further specifies atomtype along the backbone, as is the only reasonable interpreation of the author's intent.