The app is included (tracker) - it's just that full text indexing has been specifically disabled (I believe it was present in early builds). Presumably there were reasons for doing that (probably performance related, but it could be due to issues with plugins for specific file formats). Your best bet is probably to open a feature request in bugzilla to request this gets re-enabled. After that, an interface would be pretty straightforward to implement. At the least we'd hopefully get an explanation for why it was disabled in the first place.