[DeviceHome][VD] Provides webapis.sso APIs

[DeviceHome][VD] Provides webapis.sso APIs

This patch introduces 2 sso API.
 - webapis.sso.getGuid(): string;
 - webapis.sso.getOspAccessToken(clientId: string, secret: string,
       resolve: Function, reject?: Function): void;
   . reject is optional

When the 'OspAccessToken' event is emitted from WRT side to the main
thread, then, it propagates the event to the all workers. But the worker
has registered 'OspAccessToken' event can only take it.
Like as this manner, message listener can be expanded for another
purpose later.

Related chromium-efl patch:
https://review.tizen.org/gerrit/#/c/platform/framework/web/chromium-efl/+/282600/

Change-Id: I5c941e66e2729dbbeeafbbdb35a803134ed4924b
Signed-off-by: DongHyun Song <dh81.song@samsung.com>