Fix WStringStream to accept const char strings

[zachstruck-ordis]

Fix WStringStream to directly accept const char * strings.
Remove overly greedy template overload operator<<.
Remove string literal overload to reduce template bloat since there is now a const char * overload that can accept string literals.

[emweb]

Now to comment on the correct PR:

That's indeed a bit of a silly optimization. I noticed that the compiler will just optimize the strlen call out if the implementation is in the header. I updated your PR with that little change.

Regards,
Roel