* Fullscreen chat: now uses a custom page (in other words: when opening the chat in a new tab, you will have the Peertube menu). WIP
* some code refactoring (getBaseRoute moved to util/uri, ...)
Links to documentation are now using the front-end language to point to the translated documentation page
(except for some links generated from the backend, in the diagnostic tool for example).
Partial fix for #224.
