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/css/debug/comments/comments.css

@@ -0,0 +1,32 @@
+/* line 21, {pathimport}test.less */
+.tst3 {
+  color: grey;
+}
+/* line 12, {path}comments.less */
+.test1 {
+  color: black;
+}
+/* line 3, {path}comments.less */
+.test2 {
+  color: red;
+}
+@media all {
+  /* line 3, {pathimport}test.less */
+  .tst {
+    color: black;
+  }
+}
+@media all and screen {
+  /* line 3, {pathimport}test.less */
+  .tst {
+    color: red;
+  }
+  /* line 7, {pathimport}test.less */
+  .tst .tst3 {
+    color: white;
+  }
+}
+/* line 16, {pathimport}test.less */
+.tst2 {
+  color: white;
+}