Domain deletion UI
Summary:
Made on top of D2894, not merge with it for easier review.
Also includes ability to re-create a soft-deleted domain.
Test Plan: ./phpunit
Reviewers: #hkccp_developers, mollekopf
Reviewed By: #hkccp_developers, mollekopf
Subscribers: #hkccp_developers
Differential Revision: https://git.kolab.org/D2906