[COOK-3774] Environment filters

This change is to allow unmanaged hosts and services to be filtered by environment. The use case is where there is a nagios server in more than one environment, and some checks are only appropriate in one environment.

Example usage for a service that should only be checked in production:

{ 
"id": "redis_connection", 
"description": "Redis connection", 
"hostgroup_name": "redis-servers", 
"environment": "production", "command_line": 
"$USER1$/check_redis -H $HOSTADDRESS$ -p 6379"
}