Remove replication_port

Marshall replication using the primary port.

Split iproto requests into two categories: DML and admin.  Change
PING request code to 64, to lay within admin request range.
Perform administrative requests synchronously, without pushing
them into an event queue.
Add a new administrative request, IPROTO_SUBSCRIBE.

Use dynamic memory for struct iproto_request. Introduce memory
management.

Remove replication_port from the configuration file and
update tests.

Fix the test runner so that it correctly generates
replication_source to point to the primary port.
Add variable arguments to IllegalParams.
Move replia-related recovery methods to a new header, replica.h.

Remove a debug printout from box.net.lua

Update tests.
Merge branch 'master' of github.com:tarantool/tarantool
Remove replication_port from tests and server configuration files.