Added media query support.

* env.dumpLineNumbers was being lost when doing "offline" compilation
   (within node.js)
 * Added documentation for the changed options
 * --line-numbers now takes a parameter
   (either "comments", "mediaquery" or "all")
 * The system can now again output mediaqueries for FireLESS
 * Moved comments tests in debug/comments, will duplicate
   for mediaquery and for "all"

Everything is still utterly broken though, tests still fail.

test/less-test.js

@@ -46,7 +46,7 @@ runTestSet(null, "errors/", function(name, err, compiledLess) {
         sys.puts("");
     });});
     
-runTestSet({dumpLineNumbers: true}, "debug/");
+runTestSet({dumpLineNumbers: 'comments'}, "debug/comments/");
     
 function runTestSet(options, foldername, verifyFunction) {
     foldername = foldername || "";