Merge branch 'master' of https://github.com/cbhaley/calibre

Fixes #1340578 [1.44 breaks column coloring](https://bugs.launchpad.net/calibre/+bug/1340578)

src/calibre/gui2/library/models.py

@@ -55,6 +55,7 @@ class ColumnColor(object):  # {{{
         self.formatter = formatter
 
     def __call__(self, id_, key, fmt, db, color_cache, template_cache):
+        key += str(hash(fmt))
         if id_ in color_cache and key in color_cache[id_]:
             self.mi = None
             color = color_cache[id_][key]