add all used libs to the pref_about_message.

also improve the notice a bit.
s/getResourcepart().isEmpty()/isBareJid()/
Merge pull request #644 from SamWhited/barejidchecks

s/getResourcepart().isEmpty()/isBareJid()/ [EOM]
add libidn to pref_about_message.
fixed private messages
Merge pull request #645 from betheg/about_all_libs

add all used libs to the pref_about_message
formating
more refactoring for presence selection. removed getTo, getFrom and getJid from Element