Update initial condition files, update fates, new CMIP6 pop-dens, more lnd_tuning_mod options, updated ndep for fully coupled

Update the initial condition files for clm4_0, clm4_5, clm5_0 at f09_g16 for both CRUNCEpv7
forcing and GSWP3v1 forcing. Update FATES with science change to science-1.4.1_api-3.0.0.
New CMIP6 population density file that has years beyond 1850 (the old one just had 1850, so
was incorrect for historical or present-day). clm4_0 compsets now use CRUNCEPv7 forcing rather than
the CRUNCEPv4 forcing. LND_TUNING_MODE is now used for initial conditions
for different forcing. For fully coupled 1850 cases the ndep file is updated to a preliminary CMIP6
version. Fix the tools testing and build-namelist testing to work in the git checkout.