Write a very basic string extractor

Summary: Ref T1139. This has some issues and glitches, but is a reasonable initial attempt that gets some of the big pieces in. We have about 5,200 strings in Phabricator.

Test Plan: {F108261}

Reviewers: btrahan

Reviewed By: btrahan

CC: aran, chad

Maniphest Tasks: T1139

Differential Revision: https://secure.phabricator.com/D8138