Added a cap to the amount of errors you can download at once so we can never run
into the issue where there is too many errors to download at once.

Fixed a bug that was causing the nonExistentLink rule to create errors that
were not actually real.
Added a check to see if a precinct is mail only, to not check the polling locations
Merge branch 'working' into dev
Merge branch 'dev' of https://github.com/votinginfoproject/Metis into dev