Added bp_rule child notification options enforcement

This patch adds childs notification options enforcement to business rules.

The main purpose is to allow to easily build consolidated checks through business rules.

It adds two attributes named `business_rule_host_notification_options` and `business_rule_service_notification_options`. If set, all hosts/services composing the business rule will be set the `notification_options` parameter to this value.

**Example**

A cluster is composed of many hosts, all using a template from a pack allowing to check CPU usage. You want to have a consolidated notification giving the list of servers that are eating too much CPU, rather than having dozens of notifications at the same time. You may write the configuration as follows:

    define host {
        ...
        use                        ...,linux,...
        host_name                  www-001
        hostgroups                 www
        ...
    }
    define host {
        ...
        use                        ...,linux,...
        host_name                  www-002
        hostgroups                 www
        ...
    }
    ...
    define service {
        ...
        service_description                           Consolidated CPU
        check_command                                 bp_rule!g:www,Cpu
        business_rule_service_notification_options    n
        ...
    }

This will automatically set `notification_options` to `n` on all hosts of `www` hostgroup, and alert only once when at least one host eats too much CPU.