new action: dk_speakup_petition_signed
success message: add 'target' attribut to allowed_tags (for link tag)
the translation of 'signatures' was broken (for the signature counter).
this adds a plural translation in german and adds this functionality in
dk_speakup.pot.
Merge branch 'action-petition-signed'
Merge branch 'success-msg-html-tags'
Merge branch 'fix-translation-signature-plural'