Make more powerful modals

- [ ] Create a new component `modal` and wrap `modal-dialog` component inside it.
- [ ] Replace usages of `modal-dialog` with `modal`
- [ ] Close Modal when user presses `esc` key

`modal-dialog` component comes from [ember-modal-dialog](https://github.com/yapplabs/ember-modal-dialog)

Start by locating the existing `modal-dialog` component usages and read the `ember-modal-dialog` documentation linked in the issue. Add the `modal` component around `modal-dialog`, update those usages, and verify that pressing Esc closes the modal.

由索引模型根据 Issue 内容生成。