Handle process state on debugger close

[martinmcclure]

Traditional Smalltalk debuggers terminate the debugged process when closing the debugger.
Traditional non-Smalltalk debuggers (e.g. GDB) give you the choice of killing the process or detaching the debugger and allowing process to proceed.

The Sparkle debugger currently does neither -- closing the debugger pane, either by clicking on its close widget or implicitly by, for example, doing a new evaluation in the evaluator it's linked from, leaves the process suspended.

For processes that were initiated via a Sparkle evaluation, it is probably more helpful to terminate the process when the debugger closes.

Debuggers that result from attaching running processes through the process list pane should probably not terminate the process on a simple close. Leaving the process suspended may be the best choice here. The debugger has explicit terminate and proceed buttons, which also close the debugger, so those options are supported.