R1:8816f08765df

Throw instead of log for invalid properties

Summary: Continue work started at D3601.

Test Plan:
Commented declaration `AphrontController::$request`, saw exception.
Brought it back, didn't see exception.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4233