touch buttons set LED programs, added another ribbon LED program

also added PRNG

firmware/app/led/ledprog.h

@@ -9,6 +9,7 @@
 
 void lp_ribbon_init();
 void lp_ribbon_upward(uint16_t wait, uint16_t rate, uint8_t fade);
+void lp_ribbon_twinkle(uint8_t idle, uint8_t max, uint8_t thresh_lo, uint8_t thresh_hi);