new meteo-handler

• create meteo_handler_type
  • independent of global variables
  • holds all level2 information
  • cares about (dis-)aggregation of data
  • called outside of mHM in timeloop
  • methods to get forcings:
    • get_corrected_pet: get corrected PET for the current timestep and domain
    • get_temp: current surface temperature
    • get_prec: current precipitation
    • get_ssrd: current surface short-wave (solar) radiation downwards
    • get_strd: current surface long-wave (thermal) radiation downwards
    • get_tann: current annual mean surface temperature
• moved all meteo related modules in new sub-folder src/meteo/
• moved type definitions from mo_common_variables to new module mo_common_types
• add bound_error flag option to meteo namelist directories_mHM to control error rasing for meteo bound violations
• modified river temperature process class to use new meteo-handler methods