adding a new type of kinetic rate calculation, which is the sum of monod rates.
add activity model definition.
define the comon interface of activity model class.
add two classes handling Debye-Hueckel and Davies activity models
Unity activity coefficient model. All activity coefficients are ones.
small bug.
Merge branch 'reuse_trans_operator' into nitrate_test
imposing an activity model on the equilibrium reaction system.
Merge pull request #15 from HaibingShao/react_trans_GIA

React trans gia
register the process.
Merge branch 'haibing_working' into nitrate_test
proper initialization
correcting names of variables
setZero
_mat_S1_ast and _ma_S2_ast should be calculated seperately
correct names
fixing _mat_S1_orth
clean up
clean up
correct names