C-Netz: Added list of base station names and IDs

Automatic polarity detection is now done by using the polarity of last
transmitted message. We cannot use two base station IDs anymore, to
detect the polarity. Now we deal only with the defined base station ID.

src/cnetz/stations.h

@@ -0,0 +1,6 @@
+
+void init_station(void);
+void station_list(void);
+const char *get_station_name(uint8_t nat, uint8_t fuvst, uint8_t rest);
+const char *get_station_id(const char *name, uint8_t *nat, uint8_t *fuvst, uint8_t *rest);
+