Periodically log messages.

Change-Id: I86eca0c4a47e83ddb03ed569ac2cc8781760428c
Reviewed-on: http://review.couchbase.org/38873
Reviewed-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>
Reviewed-by: Pratap Chakravarthy <prataprc@couchbase.com>
Tested-by: Pratap Chakravarthy <prataprc@couchbase.com>
Few todo items.

Change-Id: Ie6a08c1002b0a163b24a294be21d45cc59065033
Reviewed-on: http://review.couchbase.org/38874
Reviewed-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>
Reviewed-by: Pratap Chakravarthy <prataprc@couchbase.com>
Tested-by: Pratap Chakravarthy <prataprc@couchbase.com>
Semantics defined for adding/updating/deleting engines.

When a new feed (aka topic) is requested to projector, full set of engines,
that are subscribed to the topic, must be provided.

Subsequently,
- use `AddEngines` to add new set of engines, providing only a subset of
  engines that are newly subscribed to the topic.
- use `UpdateEngines` to do a full update on the current set of engines, by
  providing full set of engines that need to be subscribed to the topic.
- use `DeleteEngines` to delete a subset of engines from current set, by
  providing only those engines as part of the request.

Change-Id: I80a6b1efb3492a013b2c21ed0e818e987bc0be99
Reviewed-on: http://review.couchbase.org/38875
Reviewed-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>
Reviewed-by: Pratap Chakravarthy <prataprc@couchbase.com>
Tested-by: Pratap Chakravarthy <prataprc@couchbase.com>
main program for projector.

Change-Id: I1ebbc7cf153d2bfe11b5d7981b93413fa4d1b0ad
Reviewed-on: http://review.couchbase.org/38877
Reviewed-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>
Reviewed-by: Pratap Chakravarthy <prataprc@couchbase.com>
Tested-by: Pratap Chakravarthy <prataprc@couchbase.com>