Add setMode() and setPalette() methods

- automatically start transition
Implement load FX defaults for HTTP API (FXD)

wled00/FX.h

@@ -502,6 +502,8 @@ typedef struct Segment {
     void    setCCT(uint16_t k);
     void    setOpacity(uint8_t o);
     void    setOption(uint8_t n, bool val);
+    void    setMode(uint8_t fx, bool loadDefaults = false);
+    void    setPalette(uint8_t pal);
     uint8_t differs(Segment& b) const;
     void    refreshLightCapabilities(void);