Add access and opening times to api for world offices

We render each office's access and opening times as a govspeak blob in the details hash for that office.  Yes, there will be duplication as most offices probably have the same details, but it's not clear what the alternative is for the API when it renders everything in a giant chunk anyway.
Merge pull request #575 from alphagov/access-and-opening-times-on-the-api

Add access and opening times to api for world offices
Drop legacy translated columns

These columns are no longer needed or used as they are magically made
available via the associated translations. This completes the job that
was started by https://github.com/alphagov/whitehall/pull/559
Merge pull request #565 from alphagov/drop-redundant-translated-columns

Drop legacy translated columns