Switch to using govuk_admin_template

* Start using admin gem which bundles jQuery, Bootstrap, environment indicator and default application layout
* Upgrade from Bootstrap 2 to Bootstrap 3
* Update markup to conform with newest bootstrap patterns
  * Remove most grid wrappers which were unnecessary
  * Switch from `controls` to `form-group`, and ensure there's a `form-control` class on inputs
  * Add missing `-default` classes to default buttons and alerts
  * Update modal markup, remove fade animation
* Remove all custom IE styles
* Add page titles
* Add missing H1s
* Add breadcrumbs
* Use admin template's no content styles when content is missing

## Before and after screens

### Contacts
![screen shot 2014-12-30 at 08 27 49](https://cloud.githubusercontent.com/assets/319055/5576941/a21c10e4-8ffe-11e4-8cc3-bff8ad5df1c5.png)
![screen shot 2014-12-30 at 08 28 00](https://cloud.githubusercontent.com/assets/319055/5576951/a236a350-8ffe-11e4-9144-0008d2d32716.png)

### Contact groups
![screen shot 2014-12-30 at 08 33 22](https://cloud.githubusercontent.com/assets/319055/5576942/a21c25e8-8ffe-11e4-9a8a-e4b5fd440bcb.png)
![screen shot 2014-12-30 at 08 32 59](https://cloud.githubusercontent.com/assets/319055/5576947/a22e8b3e-8ffe-11e4-96d1-ad003571e165.png)

### Editing contact
![screen shot 2014-12-30 at 08 28 19](https://cloud.githubusercontent.com/assets/319055/5576952/a23cd6ee-8ffe-11e4-89e0-2cab49dad3bd.png)
![screen shot 2014-12-30 at 08 28 33](https://cloud.githubusercontent.com/assets/319055/5576946/a2222966-8ffe-11e4-93cb-63a34cad99b5.png)

### Editing contact group
![screen shot 2014-12-30 at 08 33 36](https://cloud.githubusercontent.com/assets/319055/5576948/a22f7fb2-8ffe-11e4-9494-d401fbce6748.png)
![screen shot 2014-12-30 at 08 33 12](https://cloud.githubusercontent.com/assets/319055/5576944/a21f5de4-8ffe-11e4-8a3b-7f373fea88ce.png)

### Online links
![screen shot 2014-12-30 at 08 28 59](https://cloud.githubusercontent.com/assets/319055/5576943/a21f43c2-8ffe-11e4-9769-e3a3da550b1f.png)
![screen shot 2014-12-30 at 08 29 11](https://cloud.githubusercontent.com/assets/319055/5576945/a220cb3e-8ffe-11e4-9ff1-69c433cc557d.png)

### Editing online link
![screen shot 2014-12-30 at 08 29 56](https://cloud.githubusercontent.com/assets/319055/5576950/a236713c-8ffe-11e4-83f7-200fcdb13818.png)
![screen shot 2014-12-30 at 08 30 06](https://cloud.githubusercontent.com/assets/319055/5576949/a2327cb2-8ffe-11e4-807a-ff0b93b74aaa.png)