Add an option to write out the lat/lon of ABI obs as a netcdf

[byoung-joo]

To make some diagnostic & plotting easier
See the prototype work in branch : feature/write_abi_latlon_as_file

[byoung-joo]

It would be nice to add BT to this feature branch, because the raw obs file has Rad.

[byoung-joo]

The work from feature/write_abi_latlon_as_file is transferred to feature/write_abiahi_latlon_as_file, which is based on the current develop branch.

TODO:
make it subroutine and add a namelist option.