Adding ClientBundle

This PR adds the `ClientBundle`, or as much of it as we possibly can at this stage.

TODO:

- [x] `ApiController`
- [x] `ClientManager`
- [x] `ClientController`
- [x] `TemplateController`
- [x] `ClientEventDispatcher`
- [x] `ClientFormType`
- [x] `App.Client` backbone module
- [x] `ClientPickerType` form field (added in PR #49)
- [x] Update data fixtures for Projects so that they use a Client entity