Content pack installation state endpoint should return more information

## Expected Behavior

The endpoint that returns the content pack installation state should return more information about the entities to make it easier to list them in the UI.

## Current Behavior

Only the `id` and `type` are currently returned for entities:

```json
{
"installations": [
{
"_id": "5b55b8b73d274645e49f7eec",
"content_pack_id": "82d59d98-7440-ab74-9857-36b2f1b7ab8a",
"content_pack_revision": 1,
"parameters": {
"SOURCE": {
"type": "string",
"value": "example.com"
}
},
"entities": [
{
"id": "5b55b8b73d274645e49f7eea",
"type": "input"
}
],
"comment": "The fake input",
"created_at": "2018-07-23T11:15:03.871Z",
"created_by": "admin"
}
]
}
```