Remove Surface_Addition_Single_vdW family which is a duplicate (PR #656)

The reaction family Surface_Addition_Single_vdW is the reverse reaction of Surface_Dissociation_Beta_vdW. 
There is no need to have both families. In this PR Bjarne removed the Surface_Addition_Single_vdW 
family since we have BEP rate rules for Surface_Dissociation_Beta_vdW. 
Surface_Addition_Single_vdW had some training reactions, which he integrated into the
Surface_Dissociation_Beta_vdW to keep the data in RMG. The Surface_Addition_Single_vdW 
is not turned on by default in RMG since it is in the surface_development list of recommended.py.

See #656 for more details.

Author: rwest