When loading Trees from database, sort nodes into descending size.

This is what the comment says it was trying to do, although it may 
in fact not be the best thing to do.
When loading Trees from database, do not sort them.

We now assume that the trees are in the best possible order, 
and this is maintained manually. Sometimes you want most specific
case first, in the case of overlapping nodes, but sometimes you 
want the smallest ring first (eg. if you have cyclic transition states)
which would mean the smallest functional group definition.
Enforcing a sorting algorithm seems risky to generalize, so we now
assume the tree was in the best order, and respect that.
Remove extra spaces from thermo database saveEntry()
In transport saveEntry() remove spaces and write explicit H atoms.
Fixes to database loading and saving in order to translate it.

(Code reviewed by connie :)
Documentation for solvation is now included.

In the user guide portion of the website. Still working on
the references.
Several updates in input file documentation. Still need some edits…
Fixed transcription error for sulfur experimental Hf

Enthalpy of formation should be 65.66 kcal/mol, as in Gaussian
whitepaper.  Also added bond additivity correction for S-H
(even though it's 0).
Adding sulfur atom energies for CCSD(T)-F12.

Adding sulfur atom energies for CCSD(T)-F12a and F12b, with the
basis sets cc-pVDZ-F12, cc-pVTZ-F12 and cc-pVQZ-F12
Changing incorrect comma to colon.
Merge pull request #269 from cclass86/sulfur

Updates to sulfur thermo in statmech.py
More edits in input file documentation…
update documentation users/rmg/thermo.rst

add some images too.
move general info on RMG databases to dedicated introduction.rst file

instead of having it inside kinetics.rst.
This info also applied to thermochemistry.
update users/rmg/database/thermo.rst documentation
add parts on symmetry, chirality, QMTP file types in thermo.rst docs
add thermoEstimation module documentation

copy QMTP part in users/rmg/input.rst into the module
documentation of the thermoEstimator.
fix some minor errors in thermo docs
Redirect documentation link on heirarchical tree structures.
Fix charges and lone pairs for Helium in fromAdjacencyList() and updateCharge().

Also made calculating charges no longer redundent since it is done in updateCharge().