RGB init block - custom type

[VonSzarvas]

The current ws2812b "type" in RGB-INIT block doesn't suit all WS2812b's.

Suggest a new type in the dropdown of led types, perhaps called "custom", which allows the user to enter the values for: n0H, n0L, n1H, n1L, usReset

This would fix non-standard WS2812b LEDs, and also provide a way to make other brands of LED's work.