Refomulate Domains to Improve Sparsity

[mjohnson541]

Many of the domains in RMS aren't formulated in a form that makes the Jacobian sparse because of coupling between the dN_i/dt and V = RT/P sum_i(N_i) and dN_i/dt and P = RT/V*sum_i(N_i). This should be fixed for ConstantTPDomain in #53, but ConstantVDomain, ParameterizedVDomain, ParameterizedTPDomain, ConstantPDomain and ParameterizedPDomain still have dense Jacobians. Integrating volume and pressure (when not constant) in these equations following the template from #53 should make the other domains sparse as well. This should be relatively simple to implement. This should mostly just involve adjustments in Domain.jl, but getT, getV, getP and getC methods in Simulation.jl may need tweaked for these domains.