[Tizen][Runtime] Always use [tizen_app_id] on tizen.

For xpk, [tizen_app_id] = xwalk.[GenerateId or GenerateIdForPath]
For wgt, [tizen_app_id] = Get from config.xml

And dbus cannot take [tizen_app_id] as object path, we have
to use [package_id] as app's object path on tizen.
That is not how to write a comment.

// The [tizen_app_id] contains a dot, making it an invalid object path.
// For this reason we replace it with an underscore '_'.