Fix file change

The content of the page is not anymore deleted when the user change the
file.
Change default settings of Ace Editor

Change the tab size
Remove key binding of snippet
Improve tooltips translation
Give the focus to the editor when the window is active
Enable french translation
Remove debug data
Fix responsive paper view

Display and hide correctly the left panel
Merge pull request #126 from tdurieux/fix_web_client

Fix and improve the web client