[Foxtrot] API Changes

[Alan Lawrence]

OK, I've made a couple of changes to the APIs, which I'm afraid will no
doubt annoy those wonderful testing people, but are designed to simplify
things really (really!).

Firstly, I've got rid of the method displayWorkUnitType() in
StatusDisplayer. None of the work units I've seen ever remembered to call
it so hey :-). The replacement is a method in WorkUnit which returns a
String describing what the work unit does; the client will then display
this to the screen automatically, according to the log level (Interesting
= when the type changes, All = whenever we get a work unit).

Secondly, I've been through Result and all the classes extending it, and
standardized the order of the arguments such that "target" (the big main
number we're trying to factorise) always comes before "number" (the
subgoal). In quite a number of places these figures were getting swapped
round, which was leading to some annoying debug messages on the server and
at one point all SuccessfulResults being ignored.

Anything not clear, just ask!

--Alan