[Tizen][Runtime] Enable pause/resume web application JS engine.

The Tizen core spec requires that the web runtime should have the ability to
pause and resume the javascript engine when receiving the corresponding system
events.

BUG=XWALK-1497,XWALK-1498
Merge pull request #2217 from takethathe/jscore_pause

[Tizen][Runtime] Enable pause/resume web application JS engine.