Add XanaLink.link_type method.

sourcing/model.py

@@ -242,6 +242,10 @@ class XanaLink(Item):
     def parse(self):
         return parse_link(self.text)
 
+    @property
+    def link_type(self):
+        return self.parse()['type']
+
     def title(self, titles=None):
         if titles is None:
             titles = XanaLink.get_all_titles()