Add the rest of the major contests, .udc files and the registry

ARRL DX, IARU HF, Sweepstakes, RTTY Roundup, NAQP and general logging join
CQ WW and CQ WPX. The Cabrillo QSO line is now built column by column by the
contest, because Sweepstakes puts the callsign after the serial number where
everyone else puts it first.

User-defined contests read the subset of N1MM's .udc settings that covers the
exchange, the dupe rule, points and up to three multipliers.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/Nonemm.Contests/CabrilloExchange.cs

@@ -4,8 +4,9 @@ namespace Nonemm.Contests;
 /// carries the width it is padded to.
 public sealed record CabrilloField(string Value, int Width);
 
-/// The exchange columns of one Cabrillo QSO line, in the order the sponsor's
-/// template lists them.
+/// The columns of one Cabrillo QSO line after the time, sent group first. The
+/// callsign is one of the columns because sponsors do not agree on where it
+/// goes: most put it first, Sweepstakes puts it last.
 public sealed record CabrilloExchange(
     IReadOnlyList<CabrilloField> Sent,
     IReadOnlyList<CabrilloField> Received);