MongoDB Doc structure

Constraints
-----------

* Store initial discovery
* Identify Application setup and Store. Includes Elb and Web servers
* Store structure after caffeinate.  Includes Elb, Cafe and Web servers

Proposed structure
----------------------------
```
aws_instances
{ 
	"_id" : "i-887c77e6", 
	"Tags" : [  
		[  "webapp2",  "webapp2-sprint3" ],  
		[  "Name",  "webapp2-sprint3" ],
		...
	], 
	"PrivateIP" : "10.242.201.119", 
	"instance_id" : "i-887c77e6", 
	"webapp" : 1, 
	"Public" : [  
		"54.242.244.231",  
		"ec2-54-242-244-231.compute-1.amazonaws.com" 
	] 
}


aws_account  
{
	"application_id": 4,  
	"credentials": {  
		"access_key": "",  
		"access_token": ""  
	},  
	"instances": [  
		{instance-reference},  
		{instance-reference},  
		...  
	],  
	"date_created": Date(),
}

app_structure
{
	"application_id": 4,
	"services": [
		{
			"name": "webapp",
			"endpoint": {instance-reference},
			"cafe_nodes": [
				{
					"node": {instance-reference}
					"service_nodes": [
						{instance-reference}
					]
				} 
			]
		}
	]
}
```

All `instance-reference` will use `DbRef` feature to keep documents embedded.

topology api output :

{
	"instances" : {
		"i-887c77e6" : {
				"type" : "ELB", // ELB | CAFE | SERVER
				"Tags" : [  
					[  "webapp2",  "webapp2-sprint3" ],  
					[  "Name",  "webapp2-sprint3" ],
				], 
				"PrivateIP" : "10.242.201.119", 
				"instance_id" : "i-887c77e6", 
				"Public" : [  
					"54.242.244.231",  
					"ec2-54-242-244-231.compute-1.amazonaws.com" 
				] 
			}
		"i-8948323" : {
				"type" : "CAFE", // ELB | CAFE | SERVER
				"Tags" : [  
					[  "webapp2",  "webapp2-sprint3" ],  
					[  "Name",  "webapp2-sprint3" ],
				], 
				"PrivateIP" : "10.242.201.119", 
				"instance_id" : "i-887c77e6", 
				"Public" : [  
					"54.242.244.231",  
					"ec2-54-242-244-231.compute-1.amazonaws.com" 
				] 
			}
	},

	"topology" : {
		"i-887c77e6" : {
			"childs" : [
				"i-8948323" : {
					childs : [
						"i-4545456", 
						"i-4545457", 
						"i-4545458"
					]
				}
			]
		}
	}
}