Strip non-integers out of task id entries

Test Plan: search in task ids for t123, 456, pickles (assuming 123 and 456 exist), and you will see 123 and 456 listed. This is done in the buildQueryFromRequest function, so it would process a hand-written GET string just fine too.

Reviewers: epriestley

CC: aran, Korvin

Maniphest Tasks: T1365

Differential Revision: https://secure.phabricator.com/D2771