Added scripts in the matlab/4dvar directory

[arango]

Several new scripts were added to the matlab/4dvar repository:

• 4dvar/c_std_bry.m: creates 4D-Var open boundary conditions standard deviations NetCDF file.

• 4dvar/c_std_frc.m: creates 4D-Var surface forcing standard deviations NetCDF file.

• 4dvar/d_sst_obs.m: driver template to extract SST observations from satellite data. It creates and writes observation file. Then, it computes super observations and creates and writes super observations NetCDF file.

• 4dvar/d_std_frc.m: driver template to compute and write 4D-Var standard deviations for surface forcing.

• 4dvar/load_sst_pfeg.m: extracts satellite sea surface temperature for the period of interest and specified region from ROMS Grid file. The SST data is from the OpenDAP catalog maintained by NOAA PFEG Coastwatch in California. The resolution is 0.1 degree global 5-day average composite.

I also renamed load_ssh_data.m to a more appropriated load_ssh_aviso.m. I made minor documentation corrections to several scripts.

Many thanks to John Wilkin for providing a template for load_sst_pfeg.m.