Fixed HTML::Template objects creations (utf8 support).

HTML::Template object creations in Site.pm did not specifiy support for UTF-8
which is a trouble at least when the layouyt contains some UTF-8 encoded
characters.

I added the `utf8 => 1` parameter for both object creation (against layout and
body).

This is a duplication of commit 7467e4b901c7a881453749280632e31da94cd9d3 (I
scrambled my branches).