Clean LinboxError/LinBoxError

[Breush]

Two different general errors exist within linbox and they are both used:

• linbox/util/debug.h: class LinBoxError (which inherits from NotImplementedYet)
• linbox/util/error.h: class LinboxError (declined to things like LinboxMathInconsistentSystem)

Which one to keep?

About errors' use cases, it looks like we need:

• LinBoxError (or some generic error)
• PreconditionFailed
• NotImplementedYet
• InvalidInput (for readers)
• InconsistentSystem but others are left unused (LinboxMathDivZero, LinBoxFailure, ...)

Moreover, while cleaning, in debug.h it looks like there is a concept of Exception (BadInputException, LINBOX_RAISE_EXCEPTION etc.) that is never used.

[ClementPernet]

SolveFailed should also be considered when addressing this issue