Incorrect use of i18n in pdfcal.py

I was trying to fix an unrelated issue (issue 431) recently, when I noticed some
buggy code in pdfcal.py. It did things like

   foo_fmt = _("Bla bla: %s")
   foo = translate(foo_fmt) % something.encode('UTF-8')

translate returns a Unicode string, and the code tries to stuff it with UTF-8
data --> boom! Correct code is

   foo = _("Bla bla: $(something)")
   foo.mapping = {'something': something}
   foo = translate(foo).encode('UTF-8')

This bug is present in ST 0.11.2, SB 1.2.2 and ST trunk.

I suspect there may be other i18n related bugs in pdfcal.py, given this one, and
also issue 438. An hour spent testing pdfcal/reviewing the code would be an
hour well spent.