Chat class will give betetr error if it can not load a chat

Temporary effects last their correct durations
Changed all damage formulas to be lessl linear
Melee damage is now fully dependent of stats. A 15 STR actor wielding a mithril sword will not do devastating attacks (but still ahve pwoerful ones)
Melee/archery damage stat on weapons is renamed "power"


git-svn-id: http://svn.net-core.org/repos/t-engine4@830 51575b47-30f0-44d4-a5cc-537603b46e54