Make EEPROM storage consistent

Update ConfigurationStore to always write dummy values for disabled
options, including FWRETRACT, DELTA, and SCARA. Update the EEPROM
version to “V15.” Also fixes a buffer overrun with axis_scaling in
Config_ResetDefault.

Marlin/ConfigurationStore.h

 void Config_ResetDefault();
 
 #ifndef DISABLE_M503
-void Config_PrintSettings();
+  void Config_PrintSettings(bool forReplay=false);
 #else
-FORCE_INLINE void Config_PrintSettings() {}
+  FORCE_INLINE void Config_PrintSettings(bool forReplay=false) {}
 #endif
 
 #ifdef EEPROM_SETTINGS
-void Config_StoreSettings();
-void Config_RetrieveSettings();
+  void Config_StoreSettings();
+  void Config_RetrieveSettings();
 #else
-FORCE_INLINE void Config_StoreSettings() {}
-FORCE_INLINE void Config_RetrieveSettings() { Config_ResetDefault(); Config_PrintSettings(); }
+  FORCE_INLINE void Config_StoreSettings() {}
+  FORCE_INLINE void Config_RetrieveSettings() { Config_ResetDefault(); Config_PrintSettings(); }
 #endif
 
-#endif//CONFIG_STORE_H
+#endif // __CONFIG_STORE_H

Marlin/Marlin_main.cpp

 // M500 - stores parameters in EEPROM
 // M501 - reads parameters from EEPROM (if you need reset them after you changed them temporarily).
 // M502 - reverts to the default "factory settings".  You still need to store them in EEPROM afterwards if you want to.
-// M503 - print the current settings (from memory not from EEPROM)
+// M503 - print the current settings (from memory not from EEPROM). Use S0 to leave off headings.
 // M540 - Use S[0|1] to enable or disable the stop SD card print on endstop hit (requires ABORT_ON_ENDSTOP_HIT_FEATURE_ENABLED)
 // M600 - Pause for filament change X[pos] Y[pos] Z[relative lift] E[initial retract] L[later retract distance for removal]
 // M665 - set delta configurations
     break;
     case 503: // M503 print settings currently in memory
     {
-        Config_PrintSettings();
+        Config_PrintSettings(code_seen('S') && code_value == 0);
     }
     break;
     #ifdef ABORT_ON_ENDSTOP_HIT_FEATURE_ENABLED