Updates and fixes

Updated container insert and erase to C++11 style const_iterator parameters. (#463)
Fixed container template function overload abiguity. (#466)
Harmonize copy ctor and assignment for etl::delegate. (#465)
Added constexpr support for etl::enum_type. (#462)
Added 'make' functions to construct containers.
Remove unnecessary casts that causes warnings. (#461)
Added non-const string pointer overload. (#449)
Changed != to < in etl::ipool to get rid of erroneous clang-tidy nullptr dereference warning. (#457)
Added ifdef guard for MSVC pragma (#455)