add i_water to netcdf output and input

[jcurtis2]

For simulations being post-processed that were run with CAMP, the index of aerosol water isn't successfully found. This breaks some aspects of the post-processing pipeline (such as drying a particle population or computing critical relative humidities) and (most likely) the cloud parcel model. The issue is that aero_data_input_netcdf reads in all aerosol species names and information but aero_data_set_water_index() won't find water with its current requirements of the string needing an exact match to "H2O" where water in CAMP usually is referred to as something like aqeuous.H2O_aq. PartMC with CAMP enabled relies on the water species having a special entry in the json files of "PartMC name", which then tags the value of aero_data%i_water.

Straight forward solution is to output the value of aero_data%i_water and then also read it in instead searching the names array list.