Add new delegate entity for visualising group members in console

- Adds new `DelegateEntity` that propagates all the delegated entities sensors
- New `MEMBER_DELEGATE_CHILDREN` configuration key (default false) to enable viewing group members as children
- Enable delegates for `QuarantineGroup`
- Rendering entity sensors as links to the entity tab in the console
- Allow configurable names for delegate entities, defaults to the name of the delegated entity

![delegate-entity-sensors](https://cloud.githubusercontent.com/assets/214870/3263167/c38ff976-f26e-11e3-94ba-5e1d181dc903.png)
Image shows two groups with delegates as children, pointing to members elsewhere. The circled sensor values are entities that are rendered as HTML links to the actual entity information in the console.
Do we want this URL in the core module? Not sure how else to work it in, mind.