Support Spaces in Maniphest

Summary:
Ref T8493. Tricks:

• "Create Similar Task" and "Create Subtask" should copy the parent's Space.
• Normal list view + workboard card view.

Test Plan:

• Created a task, edited space, etc.
• Viewed tasks with different users.
• Created a "Similar Task" (saw proper Space).
• Created a subtask (saw proper Space).
• Viewed workboard.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T8493

Differential Revision: https://secure.phabricator.com/D13232