Fix unit tests for widget handler

This patch is changing the way in which manifest
and application objects are created.
All below tests now pass:
 - WidgetHandlerTest.ParseManifestWithAllOfOtherItemsAndOnePreferenceItem
 - WidgetHandlerTest.ParseManifestWithAllOfOtherItemsAndThreePreferenceItemsList
 - WidgetHandlerTest.ParseManifestWithOnlyNameAndVersion
could it be 
template\<Manifest::Type type>
base::DictionaryValue* GetPreferencesItem(int id) {
//for manifest
}

base::DictionaryValue* GetPreferencesItem\<Manifest::TYPE_WIDGET>(int id) {
// for widget
}