Fixed report not getting written to Unicode paths.

Part of issue #94.
Viewer now takes wxString URL to try avoiding encoding issues.

Part of issue #94.
Some encoding safety improvements.

However, `ToFileURL` needs to be fixed because it's giving invalid stuff
out for Unicode paths.
Fixed ToFileURL.

Turns out all that encoding stuff is unnecessary anyway, the browsers
(IE, Chrome, Firefox tested) just interpret it right anyway. Tested with
a Unicode path, part of issue #94 work.