Load LambertConformal grids from netcdf

This was required for a user loading some NOAA data via OpenDAP.
-- specifically, from a url like 'http://nomads.ncdc.noaa.gov/thredds/dodsC/narrmonthly/198801/19880101/narrmon-a_221_19880101_0000_000.grb'
-- (N.B. not currently working during US budget arguments)
This data specifies a form with a single "standard parallel".  Although PROJ4 contains a separate coding for this, it seems adequate to simply use the "two standard parallels" form with a repeated value.  Doing it that way avoids having to change Cartopy as well to make the resulting cubes plottable.