Add rgb led

Adds generic RGB leds with separate pins for anodes and cathodes. 
Pins are named by function, e.g. "red anode"->RA and "green cathode"->GC.
Origin is in middle of part. Pin ends are on 100 mil grid.
Text fields have size of 50 mils.

Related PCB footprint with pad: https://github.com/ojousima/LEDs.pretty/commit/165731ca34f827c9ddb770bc831d27994d77fa51