Character sheet now displays a diff between the previous time it was invoked...

Character sheet now displays a diff between the previous time it was invoked and the current state for even easier global comparaisons.
Total realtime playtime is now registered


git-svn-id: http://svn.net-core.org/repos/t-engine4@3639 51575b47-30f0-44d4-a5cc-537603b46e54