Use `RefreshQueue` to load search results in People list

* Prevents `Request URI too long` error on App Engine when querying for
  hundreds of IDs.
Fix paging on Admin People and Events lists

* Use `{{#each list}}` instead of `{{#list}}` to avoid rerendering the
  entire list for new pages (required a fix in `person_roles` mustache
  helper).
* Make "View More" change to "All results shown" when there are no more
  pages to display
* Fix styling of "View More" buttons
Merge pull request #712 from reciprocity/feature/fix-admin-people-search

Fix People search for large result sets