[Runtime][Tizen] Support to set app window view mode by configure
config.xml.

We support configuring application window display mode by 'display'
field in manifest.json for XPK packages. While this way is not enabled
for widget format packages.

The Widget Spec tells that 'viewmodes' attribute denotes the author's
preferred view mode.
http://www.w3.org/TR/2012/REC-widgets-20121127/#the-viewmodes-attribute

This CL enables the 'viewmodes' attribute for Widget applications.