fixes / enhancements

Fix:  #1: outputAs not being passed to onOutput callback on fatal errors
Fix:  #2: firePHP's client will abort output whene non-utf-8 encountered
Fix:  #3: objects not cloned / output() method is destructive
Enhancement:  Pass file & line number to firephp for error and warn
methods
Enhancement:  table method: "undefined" value no longer appears as null,
but as empty table cell with class t_undefined
Enhancement:  error summary at the top if there was an error
Enhancement/Fix:  boolean & null values sent to FirePHP are now sent as
boolean & null, rather than string representations