Make resolver-dnsjava, -minidns initializer

and OSGi components.

There is really no need to treat them different then
resolver-javax. This also allows the removal of the DNSUtil.init() method.
Put the AccountManager in getInstance() in the map

thereby following the code guidelines.
Don't use IQReplyFilter in AccountManager

This is a follow up on 6caf2cbdb52 where IQReplyFilter was changed so
that getUser() must not return null. But this is the case in
AccountManager where no resource binding has taken place and the user is
therefore not set.

The fix is the same as in 6caf2cbdb52, instead of IQReplyFilter we
simply use a PacketIDFilter.
Make SASLMechanism.getAuthenticationText() return byte[]

every SASL Mechanism is designed as a byte array based protocol. XMPP
adds the constraint that the challenges and responses are send base64
encoded. It's therefore better API design to let getAuthenticationText()
return byte[] instead of String.