Move the core of the browserid code into lib/

* This allows the l10n extraction tools to extract strings without traversing into subdirectories and extracting extra strings.
Getting set up for localization.

* Move all major scripts under the lib subdirectory
* add extract_po and merge_po to the scripts subdirectory
Created a create_mo.sh script.
Make sure the widget buttons are localized.

fixes #48
Get rid of the version info at the top of lib/browserid.php

Version info only belongs in /browserid.php