hints: support package and version properties.

Each property returns the value of the corresponding property for the first
entry in the package list; this is a handy short-cut for hints where there
will only ever be one package in the list (e.g. "age-days", "unblock").

Signed-off-by: Adam D. Barratt <adam@adam-barratt.org.uk>

hints.py

@@ -84,3 +84,18 @@ class Hint:
     @property
     def days(self):
         return self._days
+
+    @property
+    def package(self):
+        if self.packages:
+            return self.packages[0].package
+        else:
+            return None
+
+    @property
+    def version(self):
+        if self.packages:
+            return self.packages[0].version
+        else:
+            return None
+