add lambert conformal and gnomonic grids (GEOS5)

[bbakernoaa]

I would like to see more map projections added to NCIO. Specifically lambert conformal conic and gnomonic grids

[alex-robinson]

It's always possible to write the projection information to a file by hand (define an integer variable with the name of the grid, and then use nc_write_attr to store the projection attributes).

But it should also be easy to add these choices to the subroutine nc_write_map as well, and I would be happy to expand its capabilities. I am not familiar with the gnomonic projection - what parameter values and names should be saved in the nc file to define the projection?