Loaded component specific language strings, leaving en-GB as common fallback in case backend is in another language

When switching the backend to a different (non en-GB) language, this PR makes sure that at least en-GB is used as a fallback, to avoid strings in the config like:

![image](https://cloud.githubusercontent.com/assets/1500978/5198587/96c0526a-7518-11e4-8cdf-65216174d62f.png)