Implement ApplicationSearch in Files

Summary: Ref T2625. Ref T1163. A couple of small generalization nudges, but this is almost entirely straightforward.

Test Plan: Executed various File queries.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T1163, T2625

Differential Revision: https://secure.phabricator.com/D6091

resources/sql/patches/20130531.filekeys.sql

@@ -0,0 +1,2 @@
+ALTER TABLE {$NAMESPACE}_file.file
+  ADD KEY `key_dateCreated` (dateCreated);