Added `routing_key' parameter to publishing funcs
Edited some comments and debug messages
Fixed type for local_{hst,svc}groups list head
Added support for hostgroups routing table
Changed default values to AMQP routing settings
Code refactoring

mb_json_parse_local_hostgroups() now uses mb_json_parse_hostgroups() to
parse hostgroups array, and all hostgroups lists are now freed using
mb_free_hostgroups() function.
Added support for servicegroups routing table
Updated doc with host/servicegroup routing tables