Store user's last locale

We will use it for email and sms notifications.
Added default values to notification
Added dummy method for sending sms

Also we now log the comms effectively sent.
Added a utility method for creating a localizer

Now we can create a localizer by a locale code.
Notification service improved.

Now we have a unified interface for web, email and sms
notifications.
Please note the i18n strings still need to be explicitely
declared at some part of the code in order to be automatically
parsed.
Log unprocessed gps updates body