everywhere: use different session cookie names

If the user is hosting the dashboard in the same domain as
their blog (with a nginx suburi, for example), the two session
cookies clash; logging into one service logs you out of the other.
With this patch, both have separate names.

Fixes https://gitlab.com/commento/commento-ce/issues/49

db/20180620083655-session-token-renamme.sql

@@ -0,0 +1,5 @@
+ALTER TABLE ownerSessions
+RENAME COLUMN session TO ownerToken;
+
+ALTER TABLE commenterSessions
+RENAME COLUMN session TO commenterToken