Merge pull request #122 from qmsk/leds-format-rgbxxi

leds: artnet_leds_offset=1

leds: fix leds_format docs

leds format rgbxxi: add offset for intensities

leds format rgbxxi: avoid pixels overrun when count not divisible by group

leds: add leds_format offset for use with group

leds: rename leds_format offset -> index

leds: new RGBxxI format

leds format: refactor set_leds_pixels()

Merge pull request #120 from qmsk/leds-interface-i2s

leds: fix esp8266 build warning

leds: split i2s0/i2s1 interface stats

leds: validate I2S1 parallel

leds: support separate I2S0, I2S1 interfaces

main: only check_leds_l2s() on ESP8266