Add new CDC descriptor structs to the CDC class driver, so that the CDC demos can use human readable field names.
Rename prefix for Still Image Host class driver functions from "SImage_" to "SI_" to remain consistent with the rest of the driver.
Added new HID_ALIGN_DATA() macro to return the pre-retrieved value of a HID report item, left-aligned to a given datatype.
Added new PreviousValue to the HID Report Parser report item structure, for easy monitoring of previous report item values.