Rigel 1.7.3

* Add RTH+IRON and RTH+IRON+ZIL mining support (see `dual-rth-iron` bat/sh script)
* Add ERG+IRON and ERG+IRON+ZIL mining support (see `dual-erg-iron` bat/sh script)

Bug fixes:
* (ERG dual modes) Auto-tuner picks low dual ratios resulting in poor performance