R1:a476e5c08de9

Include symbols in main typeahead

Summary:
- Include symbols in main typeahead results.
- Simplify the symbol query a bit and extend PhabricatorOffsetPagedQuery. There was some stuff around language ranking that I got rid of, I think the theory there was that mapping file extensions to languages might not work in general but I think it works fine in practice, and we have more config stuff now around guessing languages and getting the mappings right.
- Make it easier to debug the typeahead by showing…