Set all sqlite db's to WAL mode on creation Complete work done on 6917:fba76e0bba98. WAL journaling mode now enabled on primary db as well as session db's when using sqlite for session databases. Made change to WAL mode more robust for testing by bracketing `pragma journal_mode=wal` with commit() calls. Normally the conversion would occur when a new session was opened, but this commits the changes explicitly to make all the tests stable. Also added doc on this.