Upgrade to Twitter Bootstrap 2.3.2

- upgrade vender/assets for both frontend and public apps
- moved the archivesspace javascript overrides into /app/assets to help distinguish from the vender resources
- refactor use of url() in CSS to use Rails' asset-url() to ensure paths to images are correct (required after upgrade of less-rails gem)
- move some images around in the public app and add missing icon-family image.