implement repl settings service

Change-Id: Ic39fb391b8730db8d05d327ae66da73700be5eb5

add internalSettings rest api

Conflicts:
	mock_services/mock_services.go
	replication_manager/adminport.go
	replication_manager/msg_utils.go
	tests/adminport/adminport_run.go

Change-Id: I7e546a57a57cbd35b26b9f3f2bef5685a145861a
Reviewed-on: http://review.couchbase.org/44213
Reviewed-by: Xiaomei Zhang <xiaomeizhangatwork@gmail.com>
Tested-by: Yu Sui <ysui68@gmail.com>