Resolve "Global search"

Closes #208 (closed)

aleksis/core/util/search.py

+from haystack import indexes
+
+# Not used here, but simplifies imports for apps
+Indexable = indexes.Indexable  # noqa
+
+
+class SearchIndex(indexes.SearchIndex):
+    """ Base class for search indexes on AlekSIS models
+
+    It provides a default document field caleld text and exects
+    the related model in the model attribute.
+    """
+
+    text = indexes.EdgeNgramField(document=True, use_template=True)
+
+    def get_model(self):
+        return self.model