making calls to libcloudph++ Python bindings comply with the new multi-dimensional logic
creating save_dg Python function with a probably better float32 cast logic; storing super-droplet concentration in the output netcdf file using save_sg
fixing sd_conc_mean setting + passing Courant fields to the library
Merge pull request #11 from slayoo/non-parcel

proper 2D libcloudph++ calls + storing super-droplet concentration in the output netcdf files (includes #10)