[Tizen] Dynamic Box installation support

This patch adds app-widget manifest handler.

BUG=XWALK-1515, XWALK-1516
what I meant is:
GetMandatoryValue(const base::DictionaryValue& dict,  const std::string& key, bool mandatory, bool default_value,
bool* value, base::string16* error) {
std::string tmp;
if (!GetMandatoryValue(&tmp)) // overload for string values
   return false;
return SomeStringToBoolFunction(tmp, &val);
}
GetOptionalValue(const base::DictionaryValue& dict,  const std::string& key, bool mandatory, bool default_value,
bool* value, base::string16* error) {
std::string tmp;
if (!GetOptionalValue(&tmp)) // overload for string values
   return false;
return SomeStringToBoolFunction(tmp, &val);
}
// Note: the "internal" functions are not needed