ui: add dynamic search filtering to entity lists

[aspiers]

Description

The entity lists provided by #143 are typically very long lists of people / organisations etc., and having to scroll through them is a poor UX. So we should add a search filter box which allows you to filter dynamically

Acceptance Criteria

This story can be considered done when the following acceptance tests
are satisfied:

Given a page displaying a list of entities

When I type a substring into the search filter input field

Then the list of entities dynamically updates to only show entities which contain that substring (with case insensitive matching for convenience)

Comments, Questions and Considerations

It might be worth supporting filtering based on the intersection (or union?) of multiple space-separated substrings. So if you typed foo bar into the search input field, it would only list entities which contain both (or either of?) the substring fields.

At a glance, https://github.com/enkidevs/react-search-input looks ideal for this.