Paginate environments list
Description
FE: @filipa
The environments page (/group/project/environments) currently shows all environments that exist. This is impractical long before my "create 10,000 dynamic review apps" test case.
16:37:19 gitlab-workhorse.1 | localhost:3000 [::1]:59184 - - [2016-12-09 16:36:37.249412121 +0000 GMT] "GET /root/reviewing/environments.json HTTP/1.1" 200 3309398 "http://localhost:3000/root/reviewing/environments" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:50.0) Gecko/20100101 Firefox/50.0" 41.777480Proposal
Extend the backend to support pagination, and the frontend to do pagination while respecting the different environment_type groups.