Enhanced matches for headers. Better header parsing.

Enhanced matches for headers. Better header parsing.

* Enhanced matches for headers by adding the following
  support for the suffixes .name, .address and .domain
  to header name (e.g 'From.domain' to match domain part.)
* Better header parsing, by using email.Header.decode_header
  and building a unicode string from the value returned.
  (i.e to support for example '=?iso-8859-1?q?...'.)
git-archimport-id: frederic@jolliton.com--2004-private/mail-filter--main--0.1.1--patch-1