Make all URLs truncation safe

Average users do not have a clue how to deal with long URLs that end up truncated by line return in their email client. Thus, it's really important to make the XWiki URLs truncation safe. This principle is already applied on many website, see for example StackOverflow.com

The long URL works
http://stackoverflow.com/questions/111707/zero-sql-deadlock-by-design-any-coding-patterns

But the randomly truncated also works
http://stackoverflow.com/questions/111707/zero-sql-dead

(the trick is the short identifier)