Add some C++14 type conversion typedefs to use in C++11

 Added std::remove_cv_t, remove_pointer_t, remove_const_t, remove_volatile_t, conditional_t
 Reimplemented ct_and, ct_or, etc. as template typedefs of bool_constant
Make is_iterator to control iterator category
Refactor "typename std::enable_if<>::type" to std::enable_if_t everywhere

 The same for pcomn::disable_if