Feature interface of the new c API

src/multiom/api/c/api.h

@@ -0,0 +1,17 @@
+// multio_grib2 dictionary
+int multio_grib2_dict_create( void** dict );
+int multio_grib2_dict_set( void* dict, const char* key, const char* value );
+int multio_grib2_dict_get( void* dict, const char* key, char** value );
+int multio_grib2_dict_has( void* dict, const char* key, bool* has );
+int multio_grib2_dict_iterate( void* dict, void** iterator, char** key, char** value );
+int multio_grib2_dict_destroy( void* dict );
+
+// Initialize all the options to a relevant default
+int multio_grib2_init_options( void** opt_dict );
+
+// options dict can be null, in this case default options can be applied
+int multio_grib2_encoder_open( void* opt_dict, void** multio_grib2 );
+int multio_grib2_encoder_extract_metadata( void* multio_grib2, grib_handle* grib, void** mars_dict, void** par_dict );
+int multio_grib2_encoder_encode64( void* multio_grib2, void* mars_dict, void* par_dict, double* data, size_t data_len, grib_handle* out_handle );
+int multio_grib2_encoder_encode32( void* multio_grib2, void* mars_dict, void* par_dict, float*  data, size_t data_len, grib_handle* out_handle );
+int multio_grib2_encoder_close( void* multio_grib2 );