R1:e8a213512aa0

Unprototype Spaces

Summary: Ref T8449. Also, fix annoying inconsistency between "Spaces" and "spaces": "Spaces" is the application, the things it creates are just "spaces", similar to how "Maniphest" creates "tasks".

Test Plan: Mostly reading. Viewed `/applications/`.

Reviewers: btrahan, chad

Reviewed By: chad

Subscribers: eadler, epriestley

Maniphest Tasks: T8449

Differential Revision: https://secure.phabricator.com/D13547