Modified hide operation of viewlogic

Modified hide operation of viewlogic

[Issue#] N/A
[Problem] Created webviews still remains after destorying viewlogic instance.
          This cause the application that managing multiple viewlogic instances to have huge memory
[Cause] On hiding widget (ViewLogic::hideWidget()), Viewlogic instance didn't remove existing webviews using evas_object_del()
[Solution] On hiding widget, code is modified that Viewlogic remove created webviews
[SCMRequest] N/A

Change-Id: If247a553b01dc7fe74a3bcabad31e17063233845