remove use of rust in migration (#704)

* remove use of rust in migration

rewrite use_timelines_for_feed in pure sql
delete tantivy related migration. It will require reintroducing tantivy
initialisation in docs

fix #702

* Fill timeline from migrations

should fix #692 , but probably require some testing

migrations/postgres/2019-12-10-104935_fill_timelines/down.sql

@@ -0,0 +1,8 @@
+DELETE FROM timeline WHERE id IN
+	(
+		SELECT timeline.id FROM timeline
+		INNER JOIN timeline_definition ON timeline.timeline_id = timeline_definition.id
+		WHERE timeline_definition.query LIKE 'followed or [%]' OR
+			timeline_definition.query = 'local' OR
+			timeline_definition.query = 'all'
+	);