initial port of the dedupe review UI

TODO
* At least partially integrate with existing Civi dedupe schema
* Hide left sidebar blocks on dedupe pages
* Show messages such as "nothing to assign"
* Paging does not work yet
* Improve actions UI; and some of the actions don't work.

Change-Id: I211d72f30abbff341c07ad6bef86fcc912afb4e7