#61 Botched pixel id lookup in 2.33

[Attila Kovacs]

2.33 was meant to use pixel IDs and numbers (starting from 1) interchangably. Unfortunately, it was badly implemented and resulted in unpredictable behaviour, e.g. for initial flagging, or loading pixel data. This affected all instruments except SCUBA-2 and HAWC+ (which used distinct pixel IDs that aren't simply serial numbers). Will be fixed for 2.34 starting with the beta releases (2.34-b1).