Changed main variable Hale to a static

Hale is one of the most used variables which stores the client's id of
whoever is currently Hale. It has now been hidden in boss.inc as a
static which can be accessed and set with Boss_SetBossClient,
Boss_GetBossClient, and Boss_IsClientHale(client).

Also made some other smaller variables statics inside boss.inc. More
will soon follow.