Add statistics add-in

An addin to show various statistics about Gnote.
Updated Brazilian Portuguese translation
Updated Traditional Chinese translation(Hong Kong and Taiwan)
Updated Spanish translation
Updated Czech translation
Load only enabled addins on startup

Redesign addin support so that meta information is provided by .desktop
files. Only load addin modules, when addin is enabled.
Ignore all .desktop files
Update backlinks addin to new addin support
Update bugzilla addin for new addin support
Update export to HTML addin for new addin support
Update file system sync addin to new addin support
Update fixed width addin to new addin support
Update insert timestamp addin to new addin support
Update note directory watcher addin to new addin support
Update note of the day addin to new addin support
Update print addin to new addin support
Updated replace title addin to new addin support
Update statistics addin to new addin support
Update sticky notes import addin to new addin support
Update tomboy import addin to new addin support