Fix XHTMLText.appendBrTag()

It's an empty element and not a closing one.
Use jxmpp 0.2.0

this also changes jxmpp's group from org.jivesoftware.jxmpp to org.jxmpp
Use single threaded ExecutorService

for PacketListeners. Fixes SMACK-583.
Merge branch '4.0'

Conflicts:
	smack-core/src/main/java/org/jivesoftware/smack/XMPPConnection.java
Cleanup carbons, forwarded and a few others API

Adopt to common design patterns in Smack:

- getFrom(Packet) in Packetextensions
- INSTANCES.put() in getInstanceFor()
- ELEMENT instead of ELEMENT_NAME
- Use XmlStringBuilder
Move "Message Events (XEP-22)" code to legacy

Fixes SMACK-569
Fix ExperimentalInitializer
Add SmackAndOsgiInitializer

OSGi ServiceComponents need the activate method, make sure it exists for
every SmackInitializer by using this class.
Add getDatestamp() to build.gradle
Smack 4.0.1
Smack 4.0.2-SNAPSHOT
Merge branch '4.0'

Conflicts:
	build.gradle
Add smack-java7
Fix XMPPTCPConnection to set 'host' and 'port'

Fixes SMACK-585
Add support for HostnameVerifier
Roster: merge the two registered ConnectionListeners
s/ohloh/openhub/ in README.md
Support building with Java8
Only call SimpleDataFormat once in build.gradle

re-use ext.buildDate
Add API to find services for a given feature

It's a common pattern to look for all services hosted under the users
service that provide a given feature. Let's provide an API for that and
use that API in the methods that benefit from it.