Update messages.yml

Italian translation provided.
Minor english typo corrected.
NOTE : 
Translation of : key admin_pw_required2
English and french text do not match.
English sentence does not make much sense as the french one does. Please clarify what the keys does so I will provide the ammended translation if required. In this italian translation I took for good the french one.
Please advice If changes is required.
Merge pull request #76 from bitnikrbt/patch-1

Update messages.yml - Italian translation
Updated localization for Italian

Corrected message syntax in messages.yml and added Italian to the
localization logic.
Updated test dependencies
OPDS generator will now create full URLs, see issue #80
Clear the author link form after submit and set the focus to the first field
Corrected image type for thumbnails, should be image/png
Added empty index.php to avoid directory listing
Added cache control headers for the admin area, fixes #81

Resources in this area should not be cached.
Added series number to details view, fixes issue #74

The series index of a book is now displayed in the series link in the
title details page, if available.
Version changed to 1.2.0-beta

Preparation for release.
More release preps
Updated jQuery Mobile to 1.4.0 final
Adapted install check for JQuery Mobile 1.4.0
Updated ChageLog
Made external links easier to recognize.

External links get the cloud icon.
Update messages.yml

added & fixing french translations
Merge pull request #82 from fbettocchi/patch-1

thx, will be part of the release
Debugged messages
Updated config error messages

Introduction of an updater moved to v1.3