Implement CRC16, develop mesh allocation table

- Add crc16 utility function
 - Implement CRC16 for config store, remove old checksum, increment layout version
 - Move UBL mesh store/load to MarlinSettings; increment UBL_VERSION
 - Begin to lay out MAT structure, prototype functions, etc.
 - Rename ubl.state.eeprom_storage_slot to .storage_slot
 - Misc. optimization
 - Cleanup/standardize/improve some messages

This is a work in progress!

Marlin/utility.h

@@ -25,6 +25,10 @@
 
 void safe_delay(millis_t ms);
 
+#if ENABLED(EEPROM_SETTINGS)
+  void crc16(uint16_t *crc, const void * const data, uint16_t cnt);
+#endif
+
 #if ENABLED(ULTRA_LCD)
 
   // Convert unsigned int to string with 12 format