Many changes - tidying up the extensions interfaces.

Updating the GPIO command - new command - allreadall
ScrollPhat code
max31855 code (tested with adafruit breakout board)
more tests
updated rht03 code

Raspberry Pi v3 support.

wiringPi/mcp23017.c

@@ -177,7 +177,7 @@ int mcp23017Setup (const int pinBase, const int i2cAddress)
   struct wiringPiNodeStruct *node ;
 
   if ((fd = wiringPiI2CSetup (i2cAddress)) < 0)
-    return fd ;
+    return FALSE ;
 
   wiringPiI2CWriteReg8 (fd, MCP23x17_IOCON, IOCON_INIT) ;
 
@@ -191,5 +191,5 @@ int mcp23017Setup (const int pinBase, const int i2cAddress)
   node->data2           = wiringPiI2CReadReg8 (fd, MCP23x17_OLATA) ;
   node->data3           = wiringPiI2CReadReg8 (fd, MCP23x17_OLATB) ;
 
-  return 0 ;
+  return TRUE ;
 }