[Tizen][Runtime] Fix unable to launch from a url.

The xwalk-launcher can not launch an application from a url, because of using a
wrong entry point. This patch will solve this, using the entry point
"StartURLKey" instead.

BUG=XWALK-2171
Merge pull request #2284 from takethathe/fix-xwalk-2171

[Tizen][Runtime] Fix unable to launch from a url.