Debugger: Cleanups and improvements for status notification.

Worker/Job:
- Add job listener hooks for when work actually begins for a job,
  and when a job is suspended to wait for user input.
- Add hook for setting a job description string, and implement in several
  subclasses.

LoadImageDebugInfoJob:
- Get rid of ImageDebugInfoJobListener since its functionality can be
  handled via the more general job wait for user input hook. Refactor
  accordingly.

TeamDebugger:
- Adjust to use new job hooks. When a worker job is initiated, we now
  check if the job has a description, and if so pass it on to the UI
  to display a notification.

DwarfLoadingStateHandler:
- Notify the UI when a package download is in progress.

With these changes, the status bar now notifies the user if any of the
following actions are in flight:

1) Loading/parsing debug information
2) Stack trace retrieval
3) Source code retrieval
4) Downloading a debug info package

src/apps/debugger/controllers/TeamDebugger.h

@@ -32,8 +32,7 @@ class WatchpointManager;
 
 
 class TeamDebugger : public BLooper, private UserInterfaceListener,
-	private JobListener, private ImageDebugInfoJobListener,
-	private Team::Listener {
+	private JobListener, private Team::Listener {
 public:
 	class Listener;
 
@@ -134,14 +133,12 @@ private:
 									QuitOption quitOption);
 
 	// JobListener
+	virtual	void				JobStarted(Job* job);
 	virtual	void				JobDone(Job* job);
+	virtual	void				JobWaitingForInput(Job* job);
 	virtual	void				JobFailed(Job* job);
 	virtual	void				JobAborted(Job* job);
 
-	virtual	void				ImageDebugInfoJobNeedsUserInput(Job* job,
-									ImageDebugInfoLoadingState* state);
-	virtual	void				ImageDebugInfoJobInProgress(Image* image);
-
 	// Team::Listener
 	virtual	void				ThreadStateChanged(
 									const ::Team::ThreadEvent& event);