Make SEVERITY a enum?

[laeubi]

Currently there are

 /** Constant <code>SEVERITY_WARNING=1</code> */
  int SEVERITY_WARNING = 1;

  /** Constant <code>SEVERITY_ERROR=2</code> */
  int SEVERITY_ERROR = 2;

it might be better to have these (together with INFO and probably DEBUG see #20 )as an Enum to make the code more type safe

[michael-o]

Yes, this is quite old style...