Search Symbols by Repository, not Project

Summary:
Fixes T7977.
- Move Indexed Languages and See Symbols From config to Repository
- Make symbol search skip projects

This also makes the default languages to Everything instead of Nothing.

Test Plan:
- Browse files, click symbols.
- Use quick search to find symbols
- Browse revision, click symbols

Reviewers: joshuaspence, epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Maniphest Tasks: T7977

Differential Revision: https://secure.phabricator.com/D12687

src/applications/diffusion/controller/DiffusionSymbolController.php

@@ -128,7 +128,7 @@ final class DiffusionSymbolController extends DiffusionController {
         '',
       ));
     $table->setNoDataString(
-      pht('No matching symbol could be found in any indexed project.'));
+      pht('No matching symbol could be found in any indexed repository.'));
 
     $panel = new PHUIObjectBoxView();
     $panel->setHeaderText(pht('Similar Symbols'));