small flash config improvement plus more comments

Conflicts:
	user/config.c

user/config.c

@@ -17,7 +17,7 @@ FlashConfig flashDefault = {
   "esp-link\0                       ", // hostname
   0, 0x00ffffff, 0,                    // static ip, netmask, gateway
   0,                                   // log mode
-  0,                                   // swap_uart
+  0,                                   // swap_uart (don't by default)
   1, 0,                                // tcp_enable, rssi_enable
   "\0",                                // api_key
 };

user/config.h

@@ -1,6 +1,10 @@
 #ifndef CONFIG_H
 #define CONFIG_H
 
+// Flash configuration settings. When adding new items always add them at the end and formulate
+// them such that a value of zero is an appropriate default or backwards compatible. Existing
+// modules that are upgraded will have zero in the new fields. This ensures that an upgrade does
+// not wipe out the old settings.
 typedef struct {
   uint32_t seq; // flash write sequence number
   uint16_t magic, crc;