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.
Overhaul statmech groups to include X wildcard radicals

The previous groups in statmech were created before we allowed wildcards
for radicals. As a result there were a lot of subgroups that are now
unnecessary. I have mostly deleted these groups.

Also there were a couple changes to group definitions. From the original
source of Goldsmith's thesis, it became obvious that some of the R!H atoms
types should actually be C:

-changed RdCsR2 into CdCsR2
-Moved ketone up one level from L5 to L4 was under RdCsR2
-changed RsCsR3 to CsCsC3- the way Frankling wrote the frequncies and the
symmetry number suggests it was only intended for carbons
-Changed a R!H in ketene to a C, to match the definition of ketene
-Changed name ROOH to COOH, which matches the definition
-Changed name ROOR to COOC, which matches the definition

The following groups are unclear, but I also think they should be all C:
-RsCHsR2
-CtCsR

However, I did not change anything for those two groups
Changed {2T,2S} to 2T in groups.py of statmech

Having the {2T,2S} is incompatabile for the new AdjList change. For all
these cases I changed it to 2T, as this is likely to be the ground state.

changed the following to 2T only
-"R!Hx2"
-"C_R2"
-"RsCHrr"
-"RdCrr"
-"RsCrrsR"
-"Ether"

changed "R!Hx3" to 3D only
Merge branch 'new-style-adjacency-list' of https://github.com/GreenGroup/RMG-database into new-style-silicon-hydrides
Added a new reaction library for reactions involving Si2H4.

These reaction and kinetics are from Dollet and de Persis, J. Anal. Appl.
Pyrolysis, 80 (2007) 460-470. The rates are pressure dependent and the parameters
are derived using the RRK quantum theory.
New molecule and group thermodynamic data for silicon hydrides.

The library values were found from the NIST webbook and CCCBDB. Uncertainties
were included where given. Groups were derived by Swihart and Girshick, J. Phys.
Chem. B., 1999, 103, 64-76.