library tag accessor functions

I have created functions to make it easy to get at titles and song ids
from known tags.

libsaria/sources/library.py

@@ -88,6 +88,22 @@ def albums(artist):
 		res.append( (art[key].value, key) )
 	return res
 
+def titles(artist, album):
+	art  = tag_tree[artist]
+	alb  = art[album]
+	keys = alb.keys()
+	keys.sort()
+	res = []
+	for key in keys:
+		res.append( (alb[key].value, key) )
+	return res
+
+def song_id(artist, album, title):
+	art   = tag_tree[artist]
+	alb   = art[album]
+	title = alb[title]
+	return title.keys()[0]
+
 def get_attrs(id, *attrs):
 	res = []
 	rec = tracks.get(id, None)