NitroAfrica modifications to eCLM

Modified version of eCLM developed for the NitroAfrica project. The code separates reduced and oxidised atmospheric nitrogen deposition, routes NHx and NOy to the corresponding soil mineral nitrogen pools, and adds process-based diagnostics for soil NO, N2O and NH3 emissions, including rainfall-pulse and canopy-reduction treatments. If you use this software, please cite the archived release.