logger levels

[zeratax]

At some point this new logger is probably going to be commited, but I do wonder how much the current (I assume they won't change in @hadis1000 commits) log levels make sense, do we need more and should we change current logging statements?

I assume most of us either have the logger completely on or completely off, but it would be nice to make this as sensible as possible.

enum class loglevel {
  NONE,    /**< don't log at all */
  ERROR,   /**< an ERROR which should not be ignored */
  WARNING, /**< a WARNING which might be ignored */
  INFO,    /**< a INFO which can be ignored */
  DEBUG,   /**< verbose INFO which can be ignored */
  DEBUG1   /**< verbose DEBUG which can be ignored */
};

[zeratax]

Also I think we now use neither warning nor error with #106

[visualJames]

With #109 will automatically a warning created, if error != NVRTC_SUCCESS