Remove quick create buttons from application launcher

Summary: Ref T3623. These are obsoleted by the global quick-create menu, so we can simplify the app launcher.

Test Plan: Looked at app launcher, grepped for everything.

Reviewers: chad

Reviewed By: chad

CC: chad, aran

Maniphest Tasks: T3623

Differential Revision: https://secure.phabricator.com/D8104