Recover Indexes on Indexer Restart

This is temporary code to store index metadata in a local file
and then recover those on indexer restart.

The actual metadata will come from coordinator and stream
management will be done by coordinator as well.

Change-Id: Iddf152166fd70d8fb500a9ed0bcb89265af2aa3a
Reviewed-on: http://review.couchbase.org/43540
Reviewed-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>
Tested-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>