Removed test covariance. Defined a default BC uncertainty of 2 ppm^2 in the covariance matrix. Made sure deviations in BC parameter are now relative to 0.0

added code in serial_least_squares to make surface sites do not update BC, and aircraft sites do not update fluxes

New obspack_globalviewplus.py script which replaces obspack_geocarbon.py for use with the new GV+ ObsPack product. New is the use of obs_flag so that only the (hourly) data that are considered background/representative are assimilated. Local data (obs_flag=0) are set to do-not-use.