timerange - start and end date array (in Modified Julian Days).
   type - supply an array of element centre indices.
   file - path to the output netCDF file (string).

 OUTPUT:
   FVCOM forcing netCDF file(s)

 EXAMPLE USAGE:
   init = '/path/to/output/casename_lag.nc';
   init_lag(Mobj, 1, init);

 TODO:
   Add pathlength, group and mark as arguments to the function (currently
   set to 0, 1 and 0 respectively).

 Author(s):
   Geoff Cowles (University of Massachusetts Dartmouth)
   Pierre Cazenave (Plymo