ProblemSubmissionInfo.ExecutableInfo is now created with a
LanguageDefInfo rather than a LanguageDef.
NetworkActionFactory.create now throws an IOException;
NetworkActionManager catches this IOException at createAction and prints
the stack-trace.
Fixed every single network action to make use of the new, wonderful IO
system. It will doubtless get another revamp later.
ClientMain now uses LanguageDefInfo instead of LanguageDef. With this,
the new IO system is COMPLETE - next up is making use of it to create
persistent Competitions and the likes.