fixing problems with FNMT certificates

* some people do really have no surname2. take that into account,
  and add support for that case.

* finally fix all the non-ascii chars problems with full_name. We
  are now asuming the certificate is in latin-1 and decoding that
  into unicode.
allow twitter and fnmt login at the same time
improve FNMT login error information
allow larger auth user first_name, up to 140 chars
fixing short_description error on election creation