Document additional metadata variables for broadcasting

Expanded metadata format to include additional tags for artist, title, album, year, genre, and bpm.

Author: Owen-Turnbull

source/chapters/livebroadcasting.rst

@@ -165,12 +165,17 @@ Shoutcast metadata format
 ^^^^^^^^^^^^^^^^^^^^^^^^^
 
   This allows to set custom metadata formats for the Shoutcast title field.
-  Previously only ``artist - title`` was allowed. For example if you were
-  broadcasting as part of a station, you could add the station's name or the
-  presenter's name in the title: ``MyStation | $artist - $title``.
+  Previously only ``artist - title`` was allowed. You can now use the 
+  following tags:
+  **`$artist`**, **`$title`**, **`$album`**, **`$year`**, **`$genre`**, and **`$bpm`**.
+
+  For example if you were broadcasting as part of a station, you could add 
+  the station's name or the presenter's name in the title:
+  ``MyStation | $artist - $title``.
   Or if you were doing a live mix with several artists, you could have:
   ``Live mix by MyName - currently playing: $artist``. Or even if you wanted a
-  very unusual format: ``Hey, I like $artist, here is $title by $artist``.
+  very unusual format: ``Hey, I like $artist, here is $title from the album 
+  $album by $artist``.
 
   The changes **do not** affect the case for the combination of OGG/Icecast2.