[Service][Reland] Apply node worker for standalone model

[Service][Reland] Apply node worker for standalone model

This patch includes below,

 1) unify source code with global model.
 2) isolate v8 variable scope from main thread.
   - standalone service application cannot get main global variable.
     of service_manaer / service_runner
 3) refactor handling message with node worker.
 4) refactor termination sequence of node worker more gracefully.
   - process.exit() is invoked by worker side
   - parent handles on('exit') for clean-up

Additionally, there is no noticeable memory increase with node worker.

References:
  https://review.tizen.org/gerrit/244938/
  https://review.tizen.org/gerrit/245591/

Change-Id: Ie9c17b373a69585ca755e39c4ab56243406821a2
Signed-off-by: DongHyun Song <dh81.song@samsung.com>