Added support for toggling debug mode/exposed debug mode status flag

Changes:
1. Exposed debug mode flag.
Reason- allowing monitr (https://npmjs.org/package/monitr) to send the debug mode status to process-watcher(https://npmjs.org/package/process-watcher) so that process-watcher does not kill a node worker when a debug session is in progress)

2. Added support to toggle debug mode:.
Reason- Developers need to switch in and out of debug mode on production hosts running node.