Add "Close Other Documents" to documentcontextmenu

I find this very practical, and as the documentcontextmenu isn't
exactly crowded yet ...
move parser to read, it will also be used run-time
wip create translatable strings file
more robust
Merge pull request #281 from philmassart/traduction

French translation (with new strings)
Merge pull request #279 from uliska/close-documents

Add "Close Other Documents" to documentcontextmenu
fix document context menu close other when called on a different document that the current one