[BCRSMatrix] Improve error reporting in BCRSMatrix

- Introduce new exception BCRSMatrixError and use it throughout
  BCRSMatrix
- Introduce new exception ImplicitModeOverflowExhausted, which is thrown
  by compress() for the implicit build mode. Also improve the error
  message for that exception to really help the user understand the
  problem signalled by this exception and how to remedy the situation.