R1:e711a0ed3076

Allow Pholio mocks to be destroyed with `bin/remove`

Summary: Implements the destruction interface so mocks can be permanently destroyed with `bin/remove destroy Mxxx`.

Test Plan: Destroyed some mocks.

Reviewers: chad

Reviewed By: chad

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D9551