Make smack-resolver-javax an OSGi ServiceComponent

Fixes SMACK-576
Fix PrivateDataResult.getChildElementXML()

that method never worked correctly since 11 years, ie. the PrivateData
was never added as element text. It's not surprisingly that this was not
discovered in more then a decade, since Smack usually never *sends*
those stanza but only receives them.

But that's no reason to not fix it. :)
Properly escape Bookmarks and FormField XML

by using XmlStringBuilder. Fixes SMACK-577

Also extend LazyStringBuilder with a cache. And extend XmlStringBuilder
with some more convenience methods.

Move the ELEMENT and NAMESPACE definition from Form to DataForm, where
it belongs.
Improve parseContent() and parseContentDepth()

The idea is that xml-roundtrip should *never* be expected from a
XmlPullParser. So what we need is a method that parses the content of an
element without relying on getText() returning text if on START_TAG or
END_TAG. This is already done by PubSubs ItemProvider.

Also add PacketParserUtils.parseElement() which will return the current
element as String and use this method in PubSub's ItemProvider.
Update JIRA URL
Use BufferedReader to read version
Add smack-resolver-minidns