Bug 969978 - Improve Italian keyboard layout (alternates for 'e' and '.')

* Invert é and è, since the latter is much more frequent.
* Add apostrophe and question/exclamation mark to “.”
Merge pull request #16106 from flodolo/bug969978

Bug 969978 - Improve Italian keyboard layout (alternative chars for 'e' and '.')
r=rudylu