Update pyvle according the new API of Package

- taking into account the version of VLE Without the Package singleton.
- disable pyvle_open without the specification of a package.
Remove deprecated pyvle_open function

The pvle_open() function is bad:

vpz::Vpz* pyvle_open(const char* filename)
{
  std::string logfilename = utils::Trace::getLogFilename("pyvle.log");
  std::ofstream* logfile = new std::ofstream(logfilename.c_str());
  (*logfile) << _("Error: pyvle_open whitout the specfication of a package "
          "is not possible")
                  << "\n\n" << std::flush;
}

- Memory leaks with the logfile pointer.
- The message can be view for user only if he open the
  $VLE_HOME/pyvle.log file.
- The return is missing.

So, I remove this useless function.