Implementation of the C12 + C12 rate modifications to account for
electron captures and a larger network from Chamulak et al. 2008.

Basic idea:

 -- define an ash state that consists of C13, O16, Ne20, and Na23.

    From David Chamulak:

      "If I create equal abundances of C13, O16, Ne20, and Na23 the
       mass fractions would be 13/72, 16/72, 20/72 and 23/72
       respectively. This results in the Abar, Zbar of the ash to be
       18.000 and 8.750. One can do better by taking into account the
       C12+C12 branching ratio which favors making Ne20. If you take
       the 0.6/0.4 branching ratio into account the mass fractions of
       C13, O16, Ne20 and Na23 are 0.14444, 0.26667, 0.33333,
       0.25556. This results in a Abar,Zbar of 18.000 and 8.800. If
       you use that Abar,Zbar for the ash you should have a good
       approximation as long as the temperature is below 8e8 K. If you
       look at Figure 4 in our paper you will see above 8.5e8 K Ye is
       not changing along with Y12 any more this is predominately due
       to captures on the ash becoming significant."

    By branching we note:

                      C12 + C12

                       /     \
                      /       \
                    60%       40%
                    /           \
                   /             \
             Ne20 + alpha    Na23 + p
             ----     \      ----    \
                     + C12           + C12
                         \              \
                        O16            C13
                        ---            ---

     this means that 60% of the time, we will create Ne20 + O16 and
     40% of the time we will create Na23 + C13.

     So the number of nuclei made from consuming 6 C12 is
     ~ 1.2 Ne20, 1.2 O16, 0.8 Na23, 0.8 C13.


     Doing this, the ash has an A = 18 and a Z = 8.8

     We also note that since we are operating in a high temperature
     regime, that electron captures onto Na23 (to make Ne23) have
     frozen out (see Chamulak et al.)

  -- modify the rate equation.

     Instead of 2 C12 destroyed per reaction, use 2.93 -- this captures
     the effect of a larger network.

  -- modify the energy release.

     Chamulak et al. provide the energy per reaction (and thus, energy
     release per C12 consumed), as a function of density.



