Admin pages are not displayed in browser's language

[SilasPeters]

Expected behavior

A user visiting koala, sees the webpage in the language to which the browser has been set. Thus, I would expect the same to happen when visiting koala as an admin.

Actual behavior

When visiting koala as an admin, the pages are Dutch, even though my browser is in English. When visiting koala as a member, the pages are displayed in English.

Steps to reproduce

• admin/user
• browser: firefox

Just visit the pages!

[Mstiekema]

This is not a bug, we aren't listening to browser preferences yet. There are also a few features that should be implemented before it's recommended to switch the admin language to English. See #661