Fix SimpleInhibition by removing one arg constructor
Add species diffusivity.

Add 'diffusivity' param to species, use species grids from agent
container when constructing diffusivity grid.
Refactor if statements
Move reset of species grid to 0 to fitSpeciesMassOnGrid
Fix, pass simulator to species fit
TODO FIX remove call to calculateComputationDomainGrids before agentgrid is defined
Add diffusivity to output
Prevent rock from moving
Add AcidKinetic for chemical weathering of rock.

Takes parameters described in [1], and uses eq 6.52 as rate.

[1] Bandstra, J. Z., & Brantley, S. L. (2008). Data Fitting Techniques with Applications to Mineral Dissolution Kinetics. In Kinetics of Water-Rock Interaction (pp. 211–257). New York, NY: Springer New York. doi:10.1007/978-0-387-73563-4_6
Rename temp -> T
Extract method for rate and diffRate of AcidKinetic, fix sign
Tidy up
Change AcidKinetic to expect solute to be H+ concentration
Make NaN in reaction output message a bit more sensible
Dirty fix for AcidKinetic if s=0
Add custom AcidReactionFactor, a slightly dodgy hack
Fix units of surface area
Change AcidKinetic to expect EXCESS acid, ie no bulk value
Simplify AcidKinetic to ignore alkali
Remove OH params