Debugger: Add autoDetectionSource to DebuggerItems.

This allows plugins (e.g Andoird, BlackBerry...) to control
the debuggers that are auto generated from their SDK/Target sources.

Change-Id: If5741bae0b81cff29ac6d103af6bc9a3e4399c7d
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>
Reviewed-by: David Kaspar <dkaspar@blackberry.com>
Reviewed-by: hjk <hjk121@nokiamail.com>