[WIP] Enable in-context translation support

Crowdin offers a feature to translate an application within the application itself. This PR aims to enable this with OpenProject.

There are still two bugs (which is why this is a WIP at the moment):

* [ ] The crowdin in-context localization only works for the first dev-serve request
* [ ] The crowdin language has a wierd name in the language-select box in the user settings