Simplify casting spells in the simulator.

Simplify casting spells in the simulator.

- Push more state into the simulator. This is a step towards allowing
  multiple simulators managed by Ovale.

- Remove OvaleState.now and replace with direct calls to API_GetTime().
  Places that were using OvaleState.now were really needing the current
  time, and the client already caches the current time for API_GetTime()
  for the duration of a frame.

- Re-arrange parameters to ApplySpell*() methods to simplify casting
  spells in the simulator.

git-svn-id: svn://svn.curseforge.net/wow/ovale/mainline/trunk@1205 d5049fe3-3747-40f7-a4b5-f36d6801af5f