Implemented changes to restore compilablility in clang++
* As clang currently doesn't support resolving variadic argument lists as empty in a SFINAE context the enable_if utility template is now of type size_t and expects an argument during usage (e.g. 0)
** The nicer approach of using variadic argument lists was implemented in commit d6b94cc and will be restored as soon as clang supports it
* Added new std::initializer_list based constructor to the Raw template
** Enables type safe construction
** No perfect forwarding, if this is required use of the variadic template based constructor is suggested
** Updated test cases accordingly
* Switched from c-style array to std::array in the Raw template as I found out that it satisfies std::is_pod
** has_data_member helper template now checks if Type::data satisfies std::is_pod instead of std::is_array