Rework buff duration formulas

These are derived from the client

SE_IllusionPresistence will also set the duration to 10k tics like live

utils/sql/git/required/2015_05_23_BuffDurations.sql

@@ -0,0 +1,2 @@
+ALTER TABLE `character_buffs` CHANGE COLUMN `ticsremaining` `ticsremaining` INT(11) SIGNED NOT NULL;
+ALTER TABLE `merc_buffs` CHANGE COLUMN `TicsRemaining` `TicsRemaining` INT(11) SIGNED NOT NULL DEFAULT 0;