Release of SemanticScuttle 0.88

SemanticScuttle is a social bookmarking tool (like Del.icio.us) but exploring advanced features like structured tags.

The main change of this release is the possibility to preview websites through thumbnails (thanks to artviper.net).

All the changes:
* Interface design: display SemanticScuttle version number on "about" page
* Bug fix: allow clean urls thanks to .htaccess
* New feature: add website preview/thumbnail (based on artviper.net) [Config file modified]
* Interface fix: add About link for logged users
* Interface fix: hide 'structured box' when no linked tags
* Interface fix: make more consistent the general navigation between personal and common spaces
* Interface fix: add a link to last editor profile in common description. Moreover, don't count a change if a user saves with no modifications.
* Bug fixes: prevent from adding special characters (like " or ') into tags
* Upgrade: from Scuttle 0.7.2 to SemanticScuttle 0.87.