Split Destroy/Terminate actors. Add problem checking.

I suggest squashing the commits since I know that they are slightly disorganized, and the commit messages don't always describe what's been done. Main changes are obviously:

* Separate responsibilities into Terminate and Destroy actors.
* Create `find_problems` actor method to detect issues before execution.
Ah -- the 'description' is ... but not the actual 'Actor name'. I would just throw the actor class/name in here. Ie... 'rightscale.server_array.Launch'.