Rewrite statusled implementation.

- Read it now from app.config JSON file.
- Allow for inverted status leds (Sonoff et al)
- Clean up unit tests.

unittest/Makefile

@@ -9,7 +9,7 @@ default: $(TARGET)
 all: default
 
 OBJECTS = $(patsubst %.c, %.o, $(wildcard *.c))
-SRCS    = frozen/frozen.c ../src/channel.c ../src/mqtt.c ../src/led.c
+SRCS    = frozen/frozen.c ../src/channel.c ../src/mqtt.c ../src/statusled.c
 HEADERS = $(wildcard *.h)
 
 %.o: %.c $(HEADERS)