Make message translatable
Correctly set content_type instead of deprecated mimetype
Initial read only zen mode

Preparing support for zen mode, right now it's simple read only listing
of strings.

Issue #375
Edit forms in zen mode

Issue #375
Display more unit information in zen mode (issue #375)
Include context information in zen mode (issue #375)
Dynamic loading of translations into zen mode

Now only 20 translations are loaded and additional are loaded
dynamically as user scrolls down.
Properly indicate end of translation in zen mode