Internal Firmware

This is a documented list of Internal Firmware types:
 * InternalUI Builds, which are Development/Debug builds of *OS
 * NonUI builds, which are for Factory and Development testing of *OS devices.
 * CarrierOS, which are meant for Carrier Testing.
 * Combo UI, which is a combination of InternalUI and NonUI
 * Horizon Firmware, which are stripped-down NonUI builds to recalibrate parts for iPhones.