Refactor autocomplete search

* Change `<span>` for clearing search to a `<button>`. Add
  `.link-button` CSS class to style buttons as links.
* Add Backbone view for reset button.
* Always add child views to `children` collection via `renderChild`,
  ensuring that `render` on the child is called.
* Specify `urlRoot` on `User` Backbone model. This removes coupling
  between `DeliveryForm` and `AutocompleteSearch` where `DeliveryForm`
  resets the collection of `AutocompleteSearch` after persisting the
  recipient so that the Backbone model knows what URL to `POST` to to
  create the record. Now `AutocompleteSearch` can reset the Backbone
  collection before triggering the `select` event.
* Add `onSelect` and `onReset` callbacks to customize what state the
  autocomplete input is in after selecting a result or resetting the
  search after the reset button is clicked. The default select state is
  to leave the input in a disabled state with the `value` property of
  the model backing the result.
* Add `reset` event triggered when reset button is clicked.
Display a delivery's receipts on index page

Enables a consistent display of information for different methods of
reviewing deliveries.
Switch delivery search to show all deliveries withing for pickup

Remove searching deliveries by date of delivery as it is no longer the
expected user interaction. Desk workers need, by default, a list of all
deliveries waiting to be picked up.
Add option to show all deliveries on index page

Use a `<select>` input for sorting and filtering params. Sets up a base
for filtering deliveries by deliverer, desk worker and recipient.
Add filtering by deliverer

Use `paraphrase` gem to simplify query logic.

Add constants in `DeliveryQuery` to map keywords to query param values.
This avoids hard-coding query param values throughout the codebase and
allows changing the values with minimal code churn or breaking
functionality.

Switch sorting feature test to use desk worker names to assert order
since the `appear_before` matcher finds 'UPS' and 'LaserShip' in the
`<select>` first. It isn't possible to limit the assertion to a part of
the page with `within` since the orderly gem uses `page.body` to make
the assertion[1].

[1] https://github.com/jmondo/orderly/blob/master/lib/orderly.rb#L8
Only re-render delivery search results, not entire page

Previously, the header content displaying the selected date and the
next/previous day links would need to be re-rendered when switching
days. Using a form, this isn't the case.