Now using properties files from locale folder to make localizable meta-information in install.rdf. <locale>.properties may contain keys [addon_name, addon_creator, addon_description, addon_homepageURL] to override values in package.json. Fixing bug https://bugzilla.mozilla.org/show_bug.cgi?id=661083
Cutting off others addon_* localization keys than name, creator, description, homepageURL
Improvements and fixes for localization of meta-inforation in install.rdf
Checking if key exists in localizations dict
Merge branch 'master' of https://github.com/mozilla/addon-sdk into 661083
Fix for bug 661083: "Let developers localize add-on metadata."
https://bugzilla.mozilla.org/show_bug.cgi?id=661083

The package.json keys "title", "author", "description", and "homepage"
can be localized using the property file keys "addon_title",
"addon_author", "addon_description", and "addon_homepage".

Conflicts:
	python-lib/cuddlefish/rdf.py
Bug 661083 using "extensions.<EXTENSION_ID>." instead of "addon_" as a prefix for key names
Bug 661083 adding a testaddon for the manifest localization
Merge pull request #1597 from erikvold/661083

Bug 661083 manifest localization r=@gozala