Load translation files only once

Newer versions Localization::changeLocale() already load all the
translation files, so let's avoid loading them twice.
Avoid unnecessary code

The current locale is already determined: there's no need to determine it
for packages
Don't call changelocale if not needed

If the current locale is already the wanted one, let's avoid calling Localization::changeLocale
Use the getlocale method of the section helper

...so that we'll store the last known good active locale.
Merge pull request #52 from mlocati/site-and-packages-localizations-already-loaded

Site and packages localizations already loaded