Reject high-frequency and out-of-range events during import

Summary: Ref T10747. Don't let users import SECONDLY events, or events outside of the range of a signed 32-bit integer (these are likely not too hard to support, but they're more headaches than we need right now).

Test Plan: Tried to import these no-good problem events, got helpful import errors.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10747

Differential Revision: https://secure.phabricator.com/D16716