add utf8 input back to latex

This was what we originally had in templates in Anki 1. It was changed to
utf8x at one point, then we discovered that some LaTeX installs didn't have
that package so it was removed, when we should have reverted to utf8 instead.
This fixes things like umlauts but does not allow display of things like
Japanese text.

anki/models.py

@@ -20,6 +20,7 @@ defaultModel = {
     'latexPre': """\
 \\documentclass[12pt]{article}
 \\special{papersize=3in,5in}
+\\usepackage[utf8]{inputenc}
 \\usepackage{amssymb,amsmath}
 \\pagestyle{empty}
 \\setlength{\\parindent}{0in}