Change tree in statmech groups

The previous tree did not reflect the previous definitions at all. I have
made (quite sweeping) changes to the tree to make it fit the group
definitions.

In addition I have modified some definitions for consistency:
-Add "Ketone" to "RdCsR2" ORgroup definition
-Add "Nitrites" "Nitroso" ORgroup definition
-Add "Nitrates" "Nitro" ORgroup definition

This last part has almost certinaly made some groups with overlapping
definitions. This will be fixed in later commits, presumably with the aid
of the appropraite unit tests.
Updated drawings for reaction families

I have redrawn/added ChemBioDraw pictures for all the reaction families.
They now are shown exactly as described by the adjList and have the same
atom labels (*1, *2, etc).
Re-import of NIST and training depository reactions so that dictionaries separate molecules with different atomLabels.

Hopes to fix issue https://github.com/GreenGroup/RMG-database/issues/54
Removed an import that rendered the script ineffective.
Add more detailed usage lines to importKineticsLibrary.py
Changed 1+2_Cycloaddition to only have singlets

The 1+2_Cycloaddition family can only react when the reacting biradical
has an empty orbital. Therefore we have changed all incidences of triplets
to singlets only.

Also we have forbidden triplets on the reaction site *3.
Changed 1+2_Cycloaddition family action from lose radical to lose pair

In anticipation of the new adj list change, where singlets are converted
from radical electrons to lone pairs.
Change 1,2_Insertion family to only allow singlets

1,2_Insertion cannot happen unless the reacting biradical has an empty
orbital. Changed the definition of several groups to only have 2S.

Made a forbidden group for reacting site *1 2T.

Change the lose radical action in the recipt to lose pair.
Change Disproportionation family to exclude singlets

The reaction sites *1 and *3 must have an unpaired electron to react in
disproportionation. Therefore, we have removed all instances of the 2S or
4S spin states.

We have also made forbidden groups for these cases.
Change H_Abstraction to exclude singlets where appropriate

For the H-Abstraction, the reacting site *3 must have at least one
unpaired electron. We have changed/deleted groups where 2S or 4S spin
state appeared.

We have made forbidden groups for those cases as well.
Forbade singlets in several intra-molecular reaction families

The reaction families Intra-H-migration, Intra_R_Add_Exocyclic,
Intra_R_Add_Endocyclic, Intra_Add_ExoTetCyclic need a unpaired electron to
react on the *1 reaction site.

There were no groups which violated this, but we created forbidden groups.
Changed recipe on lone_electron_pair_bond

The recipe had losing 2 radicals and gaining a lone pair. In reality, no
reaction happens. This should work correctly after the adj list changes.
Added clarifying comment to top of Oa_R_Recombination family
Change R_Addition_CSm to only react with singlets

The R_Addition_CSm family needs a unpaired electron on the 'CSm' group in
order to react. We have changed it to singlet and forbidden the triplet.
Change R_Addition_Multiple bond to react with only triplets

The R_Addition_Multiple bond family needs an unpaired electron to react.
We have removed instances of singlets on the reaction site *3.

We also added a forbidden group for the 4S case.
Change Substitution_O family to react with only triplets

The reaction site *3 must be a triplet in this family. Changed one
instance of {2S,2T} to 2S and made forbidden groups against the singlet
Change SubstitutionS family to react only with triplets

The reaction site *3 should not exist in the singlet state in this family.
Changed a few groups and added forbidden groups against the singlet.
Remove duplicate group in Disproportionation family
Remove duplicate and misplaced group in intra_H_migration family.
Removed some duplicate groups from H_Abstraction.