In the absence of time_offset, set reference basline year in netcdf o…

…utput to 0.

When setting start and end in config, interpret as beginning of year.
Example: A run with tstart = 1960 will run from 01.01.1960 with forcing assigned as 2016 in input file. With tend = 2015 the last year is 01.01.2014 to 01.01.2015with forcing from file for year 2014. The run stops at 01.01.2015.

libglimmer/glimmer_ncio.F90

@@ -240,7 +240,7 @@ subroutine glimmer_nc_createfile(outfile, model, baseline_year)
     if (present(baseline_year)) then
        sub_baseline_year = baseline_year
     else
-       sub_baseline_year = 1
+       sub_baseline_year = 0
     end if
 
     ! create new netCDF file