Add new update type to jointly assimilate Tb, SM and SCF observations in single analysis

[amfox37]

Adding a new update_type=12 that allows for the joint assimilation of SMAP/SMOS Tb, ASCAT SM, and MODIS SCF.

A relatively simple merger of existing update_type=11 and update_type=13 which first determines what species of observations are assimilated per the namelist and then loops through the tiles looking for these obs and performing the snow and/or soil moisture analysis.

As commented in the code:

    ! Loop through tiles, first apply 1d snow update, then apply 3d soil moisture update.
    !
    ! 1d snow analysis: 
    !   Update each tile separately using all observations associated with the tile.
    !   Loop through ensemble members and compute analysis separately for each ensemble member.
    !
    ! 3d soil moisture/Tskin/ght(1) analysis: 
    !   Update each tile separately using all observations within customized halo around the tile.
    !   State vector of each tile depends on assimilated obs and soil type.
    !
    !   obs             | soil    | N_state | state vector
    !   ----------------------------------------------------------------------
    !   sfcm/sfds only  | mineral |     2   | srfexc, rzexc
    !   sfcm/sfds only  | peat    |     3   | srfexc, rzexc, catdef, 
    !   sfcm/sfds & Tb  | mineral |     6   | srfexc, rzexc,         tc[x], ght(1)
    !   sfcm/sfds & Tb  | peat    |     7   | srfexc, rzexc, catdef, tc[x], ght(1)

[gmao-rreichle]

Successfully completed CONUS, GLOBAL, and GLOBALCS nightly tests after c4a1826

[biljanaorescanin]

All tests passed.