Added source browser

Added a SourceLister class, which enumerates all DVD folders below a given starting directory.
Added a source browse page to list the available sources

templates/browse/sources.tpl

@@ -0,0 +1,16 @@
+<h2>Sources</h2>
+
+{if $sources}
+	<p>
+		The following DVD sources are available to be ripped:
+	</p>
+	<ul>
+		{foreach from=$sources item=source}
+			<li>{$source|escape:'html'}</li>
+		{/foreach}
+	</ul>
+{else}
+	<p>
+		<em>There are currently no DVD sources available to rip.</em>
+	</p>
+{/if}