Introducing Smack's own XmlPullParser interface which tries to stay as
compatible as possible to XPP3. The interface is used to either wrap
StAX's XMLStreamReader if Smack is used on Java SE, and XPP3's
XmlPullParser if Smack is used on on Android.
Fixes SMACK-591.
Also introduce JUnit 5 and non-strict javadoc projects.
this is the first stop towards fixing "SMACK-65: parsing should look for
depth", by providing the initial parsing depth to the provider. Some
methods (.e.g parseMessage) now use the depth as abort condition,
instead of a unclean String equals check.
parseIQ() and parseExtension() where both renamed to parse.
This also restricts the Exceptions thrown by the parse method, to just
XmlPullParserException, IOException and SmackException (not really a big
victory, but nevertheless a slight improvement).
StreamFeatureProvider is now gone, we simply use PacketExtensionProvider
for stream features.
